Yes, the 85 mags can be used in the P-01 -- but they're larger, and will stick out. The P-01 mags won't work in the 85B (but because of the way you asked the question, I suspect you already know that).
I haven't shot the P-01, but do have a similar 75 Combat.
Except for the fact that the P-01 is a decocker version, and can't be carried cocked and locked, the two guns should feel and shoot a lot alike.
Unsolicited advice: there's no real reason to have both. In fact, I think you'd be better off with just one gun and a LOT of ammo (for practice/developing proficiency).
Or, if you've just got to have two, two of the same model, so you quickly get comfortable with just one manual of arms.
I'm not personally all that enthused about decocker versions, but that's a matter of personal preference. I DO LIKE cocked and locked.