I used to play Duke Nukem 3D, Dark forces, Comanche, WarcraftII and others in my A1200 with Falcon040/25. I have to say that OS7.x has always felt way faster than 8.x even installed in a scsi partition. I wouldn't use 8.x in my miggies again. OS8.x is quite useless and for a few apps and games OS7.x is more than enough.
I tried different 1MB rom images (650 and 900 IIRC) and it didn't make any difference.
With a graphic card Fusion3.x usually feels smoother even if you use Shapeshifter TurboEVD/MMU drivers. Fusion3.x allows using MMU for virtual memory on OS8.x IIRC. You should use Fusion 3.2 version iif you own a gfx card or Shapeshifter3.11 if you use ECS/AGA.
If you don't have an MMU there are some drivers called "AgaBoost", these had small gfx glitches but on a friend's a1200+fastram were fine to load Prince of Persia.
PS: Savage driver was the best for 030 AGA IIRC
Thanks for pre-answering MOST of the questions I had!
Just one more, how good is Basiillisk II on 68k Amigas? Any pro and cons for or against it over Fusion or Shapeshifter?