When Sergio used the technique he grew, after he left Nautillus as an employee he trained HVT style. The most impressive picture that I have seen of Sergio was when he was employed at Nautillus (the earlier pics are an example).
Casey made his best gains using HIT training, after his employ at Nautillus he went to HVT and he got smaller.
Mentzers arms, genetics again, still impressive though.
I don't use drugs, have made good gains using HIT type techniques, and don't consider my muscles 2D.
Sergio used the techniques for a short period of time. Casey never improved after turning to hit. Mentzer has some good arms but they are always there if he flexes them they are the same size. Nothing surprising happens.