Notes for the Psychics: This part will come when I finish watching all of his scenes from Tales of Fandom 2... which I, uh, haven't yet. I just want to get a better feel for what he was like in the past.
What's Okay To Mention Around Him: You can mention whatever you want around him-- if you get zapped for it, it's probably safe to say that you hit a nerve.
Abilities: Being an angel, Yuan has the full set of abilities that go with that status: a set of wings (though he keeps them hidden unless he has a good reason to reveal them), enhanced sight and hearing, incredible strength, and a lack of a need for food or sleep. Combat-wise he is a highly-skilled swordsman and a master of lightning magic.
Can I shapeshift/bodyswap/slash/etc?: Sure, but please discuss it with me first. I'm generally pretty open to anything as long as I know what I'm getting into. Slash is fine, but right now Yuan isn't interested in a relationship due to having feelings for Kratos and Jacky (and sleeping with Asch).
Maim/Murder/Death: I'd prefer no death, but like I said, if there's something you really want to do I'm willing to talk about it. (Yuan would be pretty difficult to kill anyway.)
Kissing/Hugging/Badtouch: Yuan dislikes being touched, and as such will react very badly to anyone other than Asch doing so.
Easiest way to get on his good side: If you're reasonably intelligent and sane he'll probably tolerate you just fine; whether he'll LIKE you or not is a completely different story. Yuan doesn't tend to like very many people. You'll have to really show him that you're worthy of his time.
Easiest way to get on his bad side: Yuan has a low tolerance for stupid people, nosy people, and overly-cheerful people which is why Lloyd drives him up the wall. If you're any combination of those, he's liable to ignore you or snap at you.
Favorite person: If we're talking about people that he didn't meet via the comm, then Kratos (even though he claims to hate him and tries to push him away). He actually loves Kratos and is scared of that fact.
Favorite person met on the comm: Jacky, Asch, Peony and Luke. He loves Jacky as well, but he won't admit to it for obvious reasons. Asch is currently giving him a reason to keep going, and Peony has been nothing but kind to him ever since they met. And Luke, well, he's very protective of the kid.
Prefers: Well, he can't deny it anymore-- he is most assuredly bisexual, although he does still have a preference for women.
Yuan has mellowed considerably now that Yggdrasill has been defeated and the worlds have been reunited. He's getting closer to his pre-ToS self-- which is not to say that he's not still a jerk. He can be a jerk a lot of the time; he's just less outwardly hostile now. Don't expect that temper to ever go away (as Kratos says at one point in Tales of Fandom 2, "the only straightforward thing about you is your anger"). He's still contrary and still manipulative when he wants to be, but he's less likely to be rude right off the bat.