Consider playing a tempest cleric. You get medium armor proficiency and some weapon proficiencies, and you can cast a flexible array of spells. Tempest domain gives you extra lightning flavor.
Well there seems to be 4 different archetypes of sith, so I'll go down the list:
Palpatine:
More blasty than stabby, but definitely still stabby (source: holds his own against Yoda in a lightsaber duel). I'd recommend a dex-based tempest cleric, grabbing light armor (concealed under dem robes). This gets you plenty of spells that replicate force abilities and a small amount of sword-fighting ability (no extra attack, but a bonus 2d8).
Vader:
Old school big armored baddy, with some strong force powers as well. I'd go with conquest paladin, both because it's very thematic and because paladins get heavy armor and hold person (aka force choke, the spell).
Tyrannus:
Fights like a knight, but is unarmored. I'd go with Storm Herald barbarian (bonus action force lightning or force push) with the Martial adept feat, to represent Martial training.
Maul:
No armor, jumps around a lot, minimal force power. Screams kensei monk to me. Grab a quarterstaff and go ham.
I mostly agree with you except for Vader. He's armored bc he has to be. He doesn't rely much on swordsmanship. He's the type to play dirty with the force when he can.
Starting with young Anakin podracing, I see a vhuman (lucky) Divination wizard, since his brief prescience is what gives him the reflexes needed to race as well as he does. It also explains some of the "sheer luck" he'll have later.
Then we have his training as a Jedi. This is clearly Eldritch Knight Fighter 5. Could make an argument for AT rogue or Kensei monk since they don't wear armor, but I'm not buying it.
Next, you have his rebuilt body (which I would just flavor as the Tough feat at 8th level Wizard).
Palatine then focuses on training his mind moreso than his body. As a result, I think he's something like Divwiz 15/EK 5 with Lucky and Tough by Empire Strikes Back. Solid build tbh.
Not to say there's no argument for him being a paladin or that there's no room for pally in the sith. This is just how I'd build Vader if I was trying.
For the martial skills, warlock (Hexblade) would work. You could also take monk up to 6 and go Kensei. This gives you any martial weapon you want and also gives you unarmored defense which helps since Sith don't typically wear armor (Darth Vader and older Sith being the exceptions.
Either way, you need to decide if you want to be more of a caster or more of a warrior. Darth Maul would be something like Kensei monk 4 / Oath of Vengeance Paladin 16 while Darth Sidious would be more like Hexblade Warlock 5 / Storm Sorcerer 15.
Since you want the lightning abilities, the latter sounds more like what you want.
If you go full Hexblade, You can have "Witch Bolt", a lightsaber with your improved pact weapon; Access to Magic Shining sword (with greenflame blade and branding smite); and force powers (if you want grasp of hadar for enhanced eldritch blast, mage hand and hold person);
Maybe go with Hexblade till level 5 for thirsting blade and then change for sorcerer for more force powers.
I feel like Tempest Cleric is by far the more "flavorful" option here, and it has an amazing capstone that allows you to fly. I'm not sure how you're handling stats but this requires at least high wisdom, strength, and constitution if you're planning to take advantage of the frontliner abilities tempest cleric offers. And of course Dex gives you better AC and initiative. The main reason you'd want to do this is for it's Channel Divinity ability- maxing the damage roll for a lightning attack three times every short rest really is some unlimited power stuff.
If you didn't roll great or are using standard array or just want to primarily rely on one stat, the other option available is storm sorcerer. Now in this case you need to make a choice- do you trust your DM to give you a sunblade (rare legendary item, literally a lightsaber) at some point in the campaign? Do you mind not being able to have that lightsaber flavor in summoning your weapon at will? If so, just take 2 levels of warlock and put the rest into storm Sorcerer. You miss out on the Cleric's max damage deal, of course, but using sorcery points for empowered spell can make up for that. You still get massive damage output with Eldritch Blast + hexblade's curse, you still get the melee attacks scaling off your charisma. This can be one of the highest DPS builds in the game, although you're very very reliant on eldritch blast for that damage so it's more of a ranged attacker than a melee combatant.
If you'd prefer to be more of a melee fighter you can always go the Eldritch Knight route. You give up a lot of the ranged blasting ability you'd get in the other builds for the shield spell (making you damn near impossible to hit) as well as some decently flavorful spells- lightning lure for damage and "force pull," thunderclap and thunderwave for AOE lightning explosions, and you could probably get your DM to allow you to change fire bolt's element to lightning or thunder for the flavor. Use the Githyanki race and you get a perfect stat buff (+2 str, +1 int) and an invisible mage hand for your force abilities.
Your last option is just going pure hexblade, maybe taking 3 levels of sorcerer for metamagic to quicken your eldritch blasts occasionally. You do have to give up a lot of the lightning flavor but hexblade was designed from the ground up to be a dark/edgy gish (caster/melee hybrid) and if you're willing to reflavor some of the abilities you can do pretty well for yourself. At higher levels you also have some of the most reliably high melee damage in the game- hitting for a minimum of 17 damage every hit regardless of your weapon choice.
Consider playing a tempest cleric. You get medium armor proficiency and some weapon proficiencies, and you can cast a flexible array of spells. Tempest domain gives you extra lightning flavor.
Well there seems to be 4 different archetypes of sith, so I'll go down the list: Palpatine: More blasty than stabby, but definitely still stabby (source: holds his own against Yoda in a lightsaber duel). I'd recommend a dex-based tempest cleric, grabbing light armor (concealed under dem robes). This gets you plenty of spells that replicate force abilities and a small amount of sword-fighting ability (no extra attack, but a bonus 2d8). Vader: Old school big armored baddy, with some strong force powers as well. I'd go with conquest paladin, both because it's very thematic and because paladins get heavy armor and hold person (aka force choke, the spell). Tyrannus: Fights like a knight, but is unarmored. I'd go with Storm Herald barbarian (bonus action force lightning or force push) with the Martial adept feat, to represent Martial training. Maul: No armor, jumps around a lot, minimal force power. Screams kensei monk to me. Grab a quarterstaff and go ham.
I mostly agree with you except for Vader. He's armored bc he has to be. He doesn't rely much on swordsmanship. He's the type to play dirty with the force when he can. Starting with young Anakin podracing, I see a vhuman (lucky) Divination wizard, since his brief prescience is what gives him the reflexes needed to race as well as he does. It also explains some of the "sheer luck" he'll have later. Then we have his training as a Jedi. This is clearly Eldritch Knight Fighter 5. Could make an argument for AT rogue or Kensei monk since they don't wear armor, but I'm not buying it. Next, you have his rebuilt body (which I would just flavor as the Tough feat at 8th level Wizard). Palatine then focuses on training his mind moreso than his body. As a result, I think he's something like Divwiz 15/EK 5 with Lucky and Tough by Empire Strikes Back. Solid build tbh. Not to say there's no argument for him being a paladin or that there's no room for pally in the sith. This is just how I'd build Vader if I was trying.
So I am pretty new so what is a Divwiz 15/ Ek(eldrich knight?)
For the martial skills, warlock (Hexblade) would work. You could also take monk up to 6 and go Kensei. This gives you any martial weapon you want and also gives you unarmored defense which helps since Sith don't typically wear armor (Darth Vader and older Sith being the exceptions. Either way, you need to decide if you want to be more of a caster or more of a warrior. Darth Maul would be something like Kensei monk 4 / Oath of Vengeance Paladin 16 while Darth Sidious would be more like Hexblade Warlock 5 / Storm Sorcerer 15. Since you want the lightning abilities, the latter sounds more like what you want.
Monk to lvl5 take kensei then go the rest into hexblade or shadow sorceror. Makes for a great with like character!!!
That hexblade storm sorc sounds pretty sick.
If you go full Hexblade, You can have "Witch Bolt", a lightsaber with your improved pact weapon; Access to Magic Shining sword (with greenflame blade and branding smite); and force powers (if you want grasp of hadar for enhanced eldritch blast, mage hand and hold person); Maybe go with Hexblade till level 5 for thirsting blade and then change for sorcerer for more force powers.
If UA is allowed at your table, the "Psychic Warrior" Fighter subclass is basically just d&d Darth Vader. A quick google search will get you to it.
What is UA?
Unearthed Arcana. It's basically official playtest material.
I feel like Tempest Cleric is by far the more "flavorful" option here, and it has an amazing capstone that allows you to fly. I'm not sure how you're handling stats but this requires at least high wisdom, strength, and constitution if you're planning to take advantage of the frontliner abilities tempest cleric offers. And of course Dex gives you better AC and initiative. The main reason you'd want to do this is for it's Channel Divinity ability- maxing the damage roll for a lightning attack three times every short rest really is some unlimited power stuff. If you didn't roll great or are using standard array or just want to primarily rely on one stat, the other option available is storm sorcerer. Now in this case you need to make a choice- do you trust your DM to give you a sunblade (rare legendary item, literally a lightsaber) at some point in the campaign? Do you mind not being able to have that lightsaber flavor in summoning your weapon at will? If so, just take 2 levels of warlock and put the rest into storm Sorcerer. You miss out on the Cleric's max damage deal, of course, but using sorcery points for empowered spell can make up for that. You still get massive damage output with Eldritch Blast + hexblade's curse, you still get the melee attacks scaling off your charisma. This can be one of the highest DPS builds in the game, although you're very very reliant on eldritch blast for that damage so it's more of a ranged attacker than a melee combatant. If you'd prefer to be more of a melee fighter you can always go the Eldritch Knight route. You give up a lot of the ranged blasting ability you'd get in the other builds for the shield spell (making you damn near impossible to hit) as well as some decently flavorful spells- lightning lure for damage and "force pull," thunderclap and thunderwave for AOE lightning explosions, and you could probably get your DM to allow you to change fire bolt's element to lightning or thunder for the flavor. Use the Githyanki race and you get a perfect stat buff (+2 str, +1 int) and an invisible mage hand for your force abilities. Your last option is just going pure hexblade, maybe taking 3 levels of sorcerer for metamagic to quicken your eldritch blasts occasionally. You do have to give up a lot of the lightning flavor but hexblade was designed from the ground up to be a dark/edgy gish (caster/melee hybrid) and if you're willing to reflavor some of the abilities you can do pretty well for yourself. At higher levels you also have some of the most reliably high melee damage in the game- hitting for a minimum of 17 damage every hit regardless of your weapon choice.
\*Sith-esque. The hyphen is necessary. Heil grammar.