Ok so I did some research and this is what I gathered:
Milky Housing = Gen 2 Gateron, rumour is that there is 10% chance that GMK keycaps will not have enough clearance and get caught, POM top material (more slippery).
Clear Top Regular and Clear Top SMD = Gen 3 Gateron, the issue with GMK keycaps are fixed, no clue what top material is but the clear top is the standard top now.
So people suggest get either of the clear top gen 3 versions. The black bottom one can be either plate mount of PCB mount while the SMD version is plate mount only.