I'm very open and happy to answer questions like this publicly, but thank you for your sensitivity 😊

I took 50 mg of bica once a day for two months at the very beginning of when I started E.

During that time my E dose fluctuated a lot, but I was injecting estradiol valerate in oil subcutaneously, averaging a little more than 5 mg / week total (I think a lot of that time I was taking ~2.5 mg twice a week).

When I quit bica, I increased my dose to 5 mg every 4 days or so, but kept tweaking my dose chasing more efficient and reliable T suppression. (Usually a day or two after trough I would have physiological signs of T with corresponding mental health symptoms like anhedonia, depression, anxiety, parasomnias.)

For context, when I first started HRT I was pretty neutral about my genitals and thought I had no dysphoria, but once I socially transitioned and started E, my experiences shifted (I think I had suppressed feelings from before, e.g. I experienced dissociation commonly during sex but always understood it as something other than dysphoria - now I understand it was probably caused by gender dysphoria, as a vaginoplasty has significantly improved my dissociation and other symptoms during sex).

So, almost from the start, I had it as a goal to maximize penile atrophy, and I had little interest in erections (and later esp. an active dislike and distress from erections).

All that said, I suspect the combination of bica and estrogen will absolutely risk penile atrophy, and I definitely experienced atrophy on bica + E.

Atrophy is what impacts the ability for the phallus to be erect, and in particular the spongey material to hold blood and stay hard enough for penetration. What happens is that the spongey material is a "use it or lose it" situation, and testosterone dominance causes the phallus to become erect while you are sleeping ("morning wood" is just a form of what is formally called nocturnal penile tumescence - a fancy way of saying a night time erection).

Those erections maintain the ability of the spongey material to hold blood in the future, and without involuntary night-time erections, there is a loss of that function (it can't hold as much blood, etc.).

Your mileage may vary, as is usual with HRT, but my experience with penile atrophy was that after I started HRT, I stopped having those involuntary erections when I was sleeping (mostly) and I noticed when my penis became erect, it just wasn't as "hard" as it could be before. This was maybe a bit like when you're not fully aroused when first forming an erection, but instead you couldn't get any more erect. In terms of penetration, this made it harder to feel safe when penetrating, because a semi-hard penis can sorta bend. That said, I was able to generally make it work and penetration was possible if not as safe or easy as before when the penis could get harder - but I also formed a preference for not penetrating over time, so eventually that just wasn't so relevant and I just stopped using my phallus for penetration and started treating it more like a clit (e.g. I liked to tuck it into underwear so I couldn't see it and so it would be held to my body, and then using a vibrator on it through the underwear - that helped with of the distress I increasingly felt).

I actively wanted to cultivate penile atrophy, but in the end I wasn't able to prevent erections, and my erections remained semi-hard (maybe like 70% of the original?) and still technically capable of penetration even to the end.

I occasionally would get involuntary erections, but it became a rare occurrence, and it usually bothered me significantly when they happened.

If you want to maintain function, the advice I've heard is: give yourself fully hard erections on a schedule, I would personally aim for once or twice a day to be conservative simply to replace those erections you would have had overnight. You might want to make sure the erections last long enough. I don't think orgasm is important or anything, it's just about getting the penis as hard as possible and staying that way for a bit. If you read that wikipedia article on involuntary night-time erections, it looks like the average number of erections is around 5 - 6, and the average duration of the erection is 15 - 30 minutes. You could use this to form a basis of a schedule, if you wanted - maybe try 2 erections a day maintained for 30 minutes (set a timer, use reminders and / or keep a log to track).

Another common suggestion is to rub testosterone gel / cream into the phallus and testes to help maintain their function - but whether you can tolerate the added T dose is dependent on how sensitive you are to biochemical dysphoria (I suspect T cream would have given me worse mental health symptoms, for example - I didn't ever achieve consistent freedom from those symptoms until I had my orch, fwiw).

I suspect the T cream on the testes is how trans pornstars are able to keep functioning ejaculation, etc., though it's also possible they just don't take anti-androgens and they maintain feminization through surgeries or lower dose E without T suppression? Honestly it's unclear, and I know a girl IRL who reported T-cream did not succeed in maintaining her male-style ejaculations. (Obviously you still produce ejaculate on E, it just won't be like a man's semen, it's like a clear fluid - more akin to female ejaculate.)

Hope this helps, let me know if you have any questions!