Like said Clomid is the best for hpta restart, due to having the highest binding affinity to estrogen receptors in the hypotalamus. Clomid consist of Zuclomiphene and Enclomiphene and it's the Zuclo that's giving people the estrogen type sides. So Enclomiphene shouldn't have these issues, while having the desired effects.
In practice Nolva seems to work just as well for pct though for most. It has a higher binding affinity to breast tissue, so can be used for gyno control (which may come in handy on pct), whereas Clomid does not offer protection from gyno. Nolva does lower IGF-1 some. I don't know if Clomid does too.