I'll try to answer your questions

-In the past I've been involved in some long-term 1x1 midieval fantasy settings, with humans, demons and practically anything we could come up with so I'm familiar with that. We built the world from scratch, just as we went and it was really fun. But I also think it could be interesting to have more of a modern-day setting (I was a huge fan of Charmed, a little less of the teenage shows like vampire diaries, but I could work with that kind of world too. I dislike them for the teenage part, the fantasy part is fine) 

-I did the 'gifted school' thing too, but those usually died out rather quickly because everybody was all about themselves. I don't really like playing with all teenage characters. I prefer them to be 18+, or better 20+ so they have actually develloped some character and can react reasonable instead of hormonal.

-I really like magic, but agree with you that a good set of ground rules are important. I'd rather not have every character be a half-breed, but I can work with a few of them. I'm not fond of half-breed elves, though. It's a cliché I don't often like the way they turned out. 

-I like a group growing closer together through their adventures. Romance is fine with me, so long as it doesn't exclude the other players as you're going for a small group. With groups on an adventure, I worry that some are online more frequent than others which either stalls the adventure or ends up excluding some characters. We'd have to discuss how to deal with that. 

-I would prefer having everybody play one (or maybe two) character(s) and the GM playing all the rest.