My guess is that Bank will recognize the species of the Pokemon, and adjust every other stat to fit its level based on the base stats for that species. As for gender, every Pokemon you transfer to Bank will probably be female. That’s the default gender in most battle sims, transfer hacks, etc. And with good reason.…

If you traded Pokemon Yellow’s pikachu into GSC it had a special hold item. My guess is that they WILL get hidden abilities if you transfer them up.