Concerning the ancillaries, you can have exactly 8 and not more.

For the traits I'd say there's no limitation. I once had a general with around 25 traits. I'm almost sure with that. But of course it is limited by the total number of possible traits minus the antitraits which exclude acquiring new traits.

If you were interested in a number, you would have search through the game files, and that's pretty timeconsuming.