Hi Amber,
Tough question. To me, it just happened. I'm still Fully Functional (on hops, fenugreek, maca, goat's rue, and recently flax seed and oat flakes), and feminized to the nines. Especially since the beginning of the oat flakes experiment, I wake up hard every morning, and swollen to D cups and a maca butt.
In theory, everything we do in NBE is about secondary sex characteristics. So primary sex characteristics should not be affected. There is, however, one notable exception. Dutch transsexuals traditionally (and because of a legal peculiarity) get 100 mg (!) of cyproterone acetate. They are chemically castrated within three months.
Cyproterone acetate is both a powerful progestin and a powerful anti-androgen. I don't know which of the two is the cause of the castration, but I watch out for both. My only source of progesterone is fenugreek, and I take only 2,300 mg: enough to prevent estrogen dominance, but not enough to get rounded breasts. My only 5α-reductase blocker is hops, and I take 2,500 mg: enough to prevent break outs, but not enough to prevent oily skin, and just on the edge of occasional hair loss, that can be reversed with a few weeks of minoxidil each spring.
Five years ago, I did the hard work with a vegan diet and five progressively smaller, made-to-measure, steel boned Victorian corsets. I'm still working on the muscle mass. I need the testosterone to make estrogens. The hops just blocks the path from testosterone to DHT. I use maca and walk a lot to build the muscle and the fat in my butt. I learned that from Caribbean girls in the Netherlands: they never use a bicycle or an elevator. I avoid all strength training for my arms, hands, and shoulders.
Full feminization requires a life long maintenance dose of phyto-estrogens, and possibly of anti-androgens too. I'm still looking into what that means for the risk of osteoporosis.
One of the objectives of my current experiment with oat flakes is to suppress the level of Sex Hormone Binding Globulin (SHBG) in serum. SHBG increases naturally with age. The increase limits the development of sexual characteristics later in life. So I want to control SHBG for further feminization.
I know it's not the complete answer, but I hope this helps you get on track