2 & 8 MB SIMMs do not work on the SE/30 -- just 256K, 1, 4 & 16 M 
The IIsi (and I presume the IIci too) seems to take almost anything 30 pin, parity or not, composite or not, including 2 and 8 MB sizes.
But the clearance issues aren't unique to the SE/30: the Quadra 700, for instance, has a tighter spacing between sockets, thus some SIMMs with chips on both sides won't fit.
The IIsi (and I presume the IIci too) seems to take almost anything 30 pin, parity or not, composite or not, including 2 and 8 MB sizes.
But the clearance issues aren't unique to the SE/30: the Quadra 700, for instance, has a tighter spacing between sockets, thus some SIMMs with chips on both sides won't fit.