TL;DR: Do I have to wait for the Full to sync before a completely separate hashboard in my Standard is able to mine? That seems pretty silly.
FWIW, my single standard unit was able to sync and mine at the same time.
It took it 48h roughly to sync, which is pretty good. CPU temp was in the 70s / 80s, but that should be no problem for modern chips. In fact, high end desktop CPUs can operate even close to 100C before throttling.
I would just position the thing on top of something else so it can more easily suck in air from the bottom for the little Orange Pi fan.