Penning.......In my experience, a well broke horse you don't really have to think about being under you is the best!
I have seen ex-cutters and ex-rope horses get really confused! The cutters want to always face the cattle and a rope horse has a hard time passing and turning a cow do to previous training!
A "cow" bred horse is preferred by most, but not necessary!
As for learning....just get out there and see what position you would be best at, hold back, going into the herd, the hole, wing, pusher and so on!
There are many books and videos or you could just go watch and ask questions!
A forum is a great place for tips and opinions, but somethings you got to learn in the "real world"