Happy to help! All of my knowledge is just from observing fandom spaces and reading as many fics as I can. You absorb the most by consuming the content, y'know? That's really the biggest tip I can give you. Probably not the most helpful answer because I know you're hoping for specifics. What I see and experience in the fics I read won't necessarily be the same things you see. So just, read more. Consume more. Enjoy more. That's how you get the best feel for what people enjoy. There really are no rules, no limits, no expectations other than to have fun and enjoy what you're reading and writing within the space. As for music production, best guess? Google or youtube lol. there's bound to be industry explanations and break downs for that. names too, when in doubt you can always pick an idol you don't like and just make them the villain but it's the same idea, just look up korean names and hope something jumps out at you.