You can put the SE/30 guts into a Plus, as well as just the analogue board to use with the Plus logicboard (I've done it), but the SE/30 while having a more robust power supply, is not always better as it has its own problems which may show up considering the lack of a fan in the Plus. Since it is a more robust Power board and convection continues to work the same way, I would expect it to work better, especially if you do not intend to use an internal hard drive (which MUST have a fan). The only issue would be the actual power supply is in a separate housing at the bottom of the board. So whether the metal case surrounding it, will act as a heat sink mitigating the lack of a fan or whether it will trap heat inside and overheat it, if not the system.
However, if your intent is to use the full capabilities of the SE/30 in a nicer case (sorry folks, never cared for the Snow White Compacts), then you probably shouldn't. You will definitely need that fan, though you could probably relocate it. Also you won't be able to access any PDS cards. And you will have to cut out the port connector area to accommodate the different configuration. Unfortunately a small change to the bottom of the case front prevents you from just using the SE/30 case back on the Plus front, though if you don't mind the small gap, it does otherwise fit.