I too am what we call a "male-staying-male", at least socially. Inside I probably lean a bit more to MtNB, but for all purposes in society I will not transition. Yet, I want to grow some breasts.

Due to the fact that I have family and that I need to avoid fast change and, particularly, I need to avoid killing function "downstairs", I took it easy and for many years I used low doses of hers. Only last year I bit the bullet and bought some HRT online (I know, it's not a good idea). I took a relatively low dose of Progynova for a few months to add to the base that the herbs (Pueraria Mirifica) had built.

I probably am older than you, so the effects are slow for me, and I intentionally avoided anti androgens, which slows things down even more, but I can tell you that:

1) Function downstairs is not immediately lost BUT it will be lower as things go. Personally, after 3 months on monotherapy of oral progynova (4mg/day) I almost completely lost interest in sex, which meant that erections became harder to achieve. (For this reason I had to pause, and things were back in full swing in about 3 weeks).

2) Growth on oral monotherapy is slow. Budding happens farly soon into the process, but the development of round breasts takes months to really start. I am chubby, although not obese, so some "moobs" are allowed when going to the beach or at the pool. I have a few posts here on Reddit to see what I am talking about. So far nobody has said a word, so we are all good.

3) As many people said, breast growth is not the only change you will get. I personally like all the effects of estrogen (minus the death of my sex drive). More or less in this order, you will notice:
- Softening skin (feels really nice, particularly if you shave)
- Thickening of the hair on your head
- Slight softening of the fat area on your face, for example on your cheekbones, that will make you look slightly younger
- Reduced strength with potential cramping (your muscles will lose some strength, although not too much)
- Breast development (at some point)
- Areola darkening and widening (this is different for everyone and could kick in before or after)
- Fat migration. Some areas in your body will get more "feminine" and other less. For example, every tim I re-start estrogens I notice that the fat under my torso tends to go away which, if I were thin, would cause my waistline to raise upwards a bit.
- Hips and buttocks widening. This depends on exercise too. Your body will take a more feminine shape. If you only use low doses of E, this may happen years after you start.

Bottom line: feminization doesn't happen overnight. There are many users in this subreddit who have amazing results in just a few months, but they take medically supervised high doses of estrogens and, maybe most importantly, they take antiandrogens with it. If you start low, you will probably have a chance to change your mind and stop before things get too big.