I've tried a lot of the MacOS versions, but I skipped a lot of them, after some testing.
68030 16/33Mhz: 7.5. 8.1 was possible with my 68LC40 accelerator, but it ran miserably on 10MB of RAM.
68040 33Mhz: 7.5, 8.1 was notably slower.
603ev 180/225Mhz: dual boot 7.6 and 8.6. 9.1 ran slower, DooM...