Drive back cap
Most people that call them VX'd when they upgrade just the VX drive. A good amount also have the gold bolt and the green VX detents. It is not typical to see the reg / back cap changed. Sometimes you will see the feedneck changed, but again, not enough to call it a regular change to a "VX'd" Clone.
Both V1/2 clones can be VX'd. The only differences in the V2 were the valve keg, grips, detents (V2/VX detents are still different though, 3 total versions) and feedneck screw.
None of it really matters because a vx'd (gold bolt and vx drive) clone shoots identical to an actual vx. I don't really care for the vx or rx reg, I like the v1/2 feedneck better than the vx, the v1/v2 typically have a "type a" screen on the board which is a $30 change when it fails (it's replace with a flash and a "type b" screen, the type 1/2 milling on the back cap is purely aesthetics and the v1/2s came in prettier colors.
Basically what I'm saying is clones are amazing regardless of the version... get one and make sure the internals are up-to-date and that you have the new militia lube and enjoy.
I was sold a "v2" clone and it had vx detents, v2 grips, and feedneck screw but it came with a v1 valve keg. I have yet to see any wear on the valve o-rings so far, and it shoots great. I might get a gold bolt but won't get a vx drive until I see a problem.