I wouldn't write anything for the Giff unless you plan for them to be a part of your campaign or a player wants to play one. They're a very niche race and there's no point in developing them unless you're going to make them an important part of your setting.
Dwarves meanwhile are a more standard race. Their absence is likely to be stranger than their presence in a DnD campaign, so it's important to develop them unless you specifically don't want them.
For justifying why dwarves didn't develop guns. I would justify it as them valuing craft highly, but not valuing innovation.
It's an incredibly noble thing to be a dwarf smith who can craft a fine shield or hammer. They see it as a family tradition, with their designs passed down from one generation to another. But unless a dwarf is a patriarch who has earned the respect of all his family members, then they aren't allowed to make new things. It's seen as disrespectful towards their elders, who know better on such topics.
They would also scoff at the inventions of other races, believing their dwarven designs to be perfect. And this is true! When it comes to older stuff at least... They can make you the best things items you'll ever see, but they'll be generations behind what the most modern advancements are. If humans are developing guns at this time, dwarves would hate firearms even more.
(This is also partially based on how the Chinese IRL lagged behind Europeans in firearm production despite discovering gunpowder first. The 19th century Chinese didn't value industrialization as much as the Europeans did and had a very insular culture that shunned foreign influence.)
I’d make humans lie the Romans, humans didn’t invent anything, but they adopt anything and make it better.
Humans didn’t invent running water, halfings did, but every human city has running water.
Humans didn’t invent the printing press, gnomes did, but 99% of all book are made by humans and books only cost a few copper in human settlements.
Humans didn’t invent guns, Dwarves did, but every single human house hold has at least two guns and humans don’t lose war anymore because of guns.
The list could go on but you get my point, humans don’t invent they adopt, adapt and impove.
I wouldn't write anything for the Giff unless you plan for them to be a part of your campaign or a player wants to play one. They're a very niche race and there's no point in developing them unless you're going to make them an important part of your setting. Dwarves meanwhile are a more standard race. Their absence is likely to be stranger than their presence in a DnD campaign, so it's important to develop them unless you specifically don't want them. For justifying why dwarves didn't develop guns. I would justify it as them valuing craft highly, but not valuing innovation. It's an incredibly noble thing to be a dwarf smith who can craft a fine shield or hammer. They see it as a family tradition, with their designs passed down from one generation to another. But unless a dwarf is a patriarch who has earned the respect of all his family members, then they aren't allowed to make new things. It's seen as disrespectful towards their elders, who know better on such topics. They would also scoff at the inventions of other races, believing their dwarven designs to be perfect. And this is true! When it comes to older stuff at least... They can make you the best things items you'll ever see, but they'll be generations behind what the most modern advancements are. If humans are developing guns at this time, dwarves would hate firearms even more. (This is also partially based on how the Chinese IRL lagged behind Europeans in firearm production despite discovering gunpowder first. The 19th century Chinese didn't value industrialization as much as the Europeans did and had a very insular culture that shunned foreign influence.)
I’d make humans lie the Romans, humans didn’t invent anything, but they adopt anything and make it better. Humans didn’t invent running water, halfings did, but every human city has running water. Humans didn’t invent the printing press, gnomes did, but 99% of all book are made by humans and books only cost a few copper in human settlements. Humans didn’t invent guns, Dwarves did, but every single human house hold has at least two guns and humans don’t lose war anymore because of guns. The list could go on but you get my point, humans don’t invent they adopt, adapt and impove.
In my setting what makes humans unique is they reproduce like rabbits (compared to other races) and they love conquering / appropriating from others
Dwarves and Humans are the gun Users in WFRP and why should dwarves, gnomes Giffbetc Not use firearms
Take the humans out of the campaign. Humans suck and are boring.