PM alone wont do much, its slower and feels "dirtier" in a way. It can badly mess up stuff if used on too high dose. Slow gradual changes, likely no over all feminisation. Function will very likely return to normal or not suffer much at all. Don't expect big results. Combined with other things it can be somewhat effective.
HRT is the thing that does it, but it does everything, not just boobs. On higher dosages and or longer term its almost guaranteed to nuke the ability and junk can shrink. Changes are often permanent but typically function returns if its stopped. Keep in mind HRT can badly fuck up XY cis male brain. Thought processes and moods can go totally haywire. This is 100% individual thing however, some get almost no mood swings or changes with mind stuff while others get a complete rewiring of everything.
Both can work, both can turn out bad if not done right. I also advice not to go on HRT for wrong reasons, its not to be toyed with. Then again, herbal stuff is strong and not to be toyed with either. Its likely safer route for cis guy wanting some changes but not the whole thing.