Badin, Trotwood-Madison, Mt. Healthy, Butler are all top 8 seeds from last season in D3 R12 that have moved up to D2 R8. Elida, New Richmond, and Oakwood are also lower seed playoff teams from last year that departed D3 R12 for D4. This region will certainly have a much different feel this upcoming year, so that'll be interesting.
This is all alphabetical order, but below is who I'd expect to be contending for the top 8 seeds. The next group below that are what I'd consider contenders for playoff berth and potentially a top 8 seed. Out of this region in general, my initial thoughts would assume that: Bellefontaine, Wapakoneta, Tippecanoe, and Archbishop McNicholas are the most likely teams to win the region.
Archbishop McNicholas
Bellbrook
Bellefontaine
Chaminade-Julienne
London
St Marys Memorial
Tippecanoe
Wapakoneta
Celina
Hillsboro
Miami Trace
Ross
Western Brown