The ROMs are on SIMMs so getting a B or C revision is not an issue. I upgraded one of mine to a later revision just so slave drives on the IDE bus worked. I think there are also issues between revisions and OSX compatability, but I run 9.x so it doesn't bother me.

Any of the personality cards should work in any boards, I have the A/V ones in both of my beige G3s.

I think both of my units were 233 G3s with 512K cache and I upgraded one to a 433/1MB and the other to a 300/1M just because the full 1MB cache which speeds things up.