Two cat questions inside one post ?

Well, if Otis is a stray and Vera is a domestic cat, then it's normal for them to behave differently. Otis sounds like he's got a little "wild" in him. It it totally normal for kittens to play like that. However, if they're not better adjusted to each other in a few weeks, then I think it would be best to re-home one of them. Otherwise they'll constantly hate each other.