As far as I can tell, there is no way to find out what the previous coach ran, unless you can find him and ask him. In the case of a sim-coached team, they seem to generally run pro-set and I, but I have had used all six sets against me in a game once.
You are not necessarily forced into a single back set. I started 2 freshman RBs in a wishbone last year with some success. It depends upon what you can recruit, obviously, but sometimes you can get freshmen RBs who can contribute right away.