Well, MOST 8ns ram is in the PC-100 family, so as long as it is UNBUFFERED, and fits the slots, it should work. It will just run at the slower speed.
Most 10ns ram is in the PC-66 family which is what the Beige G3's were spec'd for anyway. The only bad thing that could happen is that the machine will not boot if the ram is not compatible, or if it does boot, could start producing memory address errors, in which case you just remove it and everything will be back to normal.
Just be sure the check some other sources to verify what type of ram it actually is before installing it.