Monitors You can interchange monitors, but you will have to tweak those with fixed horizontal scan rates. High-Res Mono monitors are directly interchangeable. ROM is wildly different. It works for us in the one case we tried, but there may be some specific board revs that cause incompatabilities. I've given up and put it in my SS1 for the time being.
Mice are interchangeable to some extent.
Video FrameBuffers There is no interchangeability here. Sun frame buffers are also not usable in the Solbourne boxes.