Dr. Saya has stated that Clomid—clomiphene—is more effective than Nolvadex—tamoxifen—for HPTA stimulation. I'll go a step further and say that the enclomiphene component of clomiphene is even better by itself. The zuclomiphene component of clomiphene is estrogenic and works against HPTA activation. I've been using enclomiphene for most of the year with no negative effects. I consider it the drug of choice for this sort of thing. Use Clomid if you have to, but not if you can get a doctor to write a prescription for enclomiphene.
Proviron, aka mesterolone, is somewhat suppressive. It causes negative feedback at the hypothalamus. I'd avoid it if possible. It's true that Clomid can raise SHBG substantially. But this is due to the zuclomiphene. Enclomiphene alone does not do this.