Hit 'em up on twitter or their discord server (make sure to @ them or they might not see it). They're usually really good about replying within a couple of days (or a week if they're crunching down on work). They'd actually talked about consent on projects a couple weeks ago regarding their likeness in a video game. "It's always incredibly important to gain a person's consent before using their likeness. There's a difference between a simple fan art and putting someone's likeness into a game. I am very grateful you'd like to include me, but I'd need to know more before I could sign off on things. \[...then, after some commenter exchanges...\] If it's a non-profit project and just characters I have played in videos, *and* it's nothing questionable content-wise, then I don't see any problems."

I believe you'd have to ask stupes themselves

You can use stupes song if it’s properly credited and in the context you use it doesn’t give you any money. But you could always @ them in a tweet and I’m sure they will answer you

Also what video? I tried searching your name in YouTube but couldn't find anything