The AI avatars have different strengths and bonuses, is your avatar forced to be "vanilla" when you play them or are your strengths carried over from your Ai persona? Doesn't seem fair that the AI gets 10% science and faster units for example and the player gets nothing.

Your traits only apply when your avatar is used as an AI yes, not when you are playing it

You can use avatars of other players who dont have traits if you want

There is no way to get extra bonuses with traits as the player,