As a rule of thumb you can never run an earlier OS on a machine - the one it shipped with is as early as it goes. Only someone who knows all the internals of Mac OS - i.e. an Apple engineer - could do it, and even then the machine would have to have a very similar hardware architecture to other Macs that are supported by the earlier OS.
FWIW, OS 9 absolutely screams on every G3/300 or faster Mac I've ever used it on. On such machines I doubt any OS7 variant would be faster - and might even be slower because of the amount of 68k code that's still left even in 7.6.1.
Finally, I imagine one could install Kaleidoscope in OS 9 and use it to theme the OS to look like OS7.x.
Best,
Matt
FWIW, OS 9 absolutely screams on every G3/300 or faster Mac I've ever used it on. On such machines I doubt any OS7 variant would be faster - and might even be slower because of the amount of 68k code that's still left even in 7.6.1.
Finally, I imagine one could install Kaleidoscope in OS 9 and use it to theme the OS to look like OS7.x.
Best,
Matt