I will try the easier part. If Evina returns there will probably not be any incoming transfers, because that is 14 and IMO Autumn probably deserves a free ride in future years, and I hope she gets it.
Having said that, my guess is Evina doesn't return, so you could add Autumn and still have one open spot. I don't think that means you have to fill it, and remember that potential 15th player could be using up a roster spot for three more years, so better not to use it unless it is a transfer at least at Evina or say Azura's level.
I see potential incoming transfers as more filler to plug holes off the bench from unanticipated outgoing transfers. When you get a surprise announcement of a departure, it is generally too late to fill that need with a recruit in the next incoming class. But with transfers probably becoming immediately eligible, it can be easily be done with the transfer portal, at least for a bench player needed at a certain position.
So keep track of them more on a contingency basis, and be ready to strike when someone departs. But if everybody stays, there is no room at the Inn!
