also like... I had this exact feeling, I was like "oh shit I think I might be a woman, but idk if I want boobs? like i might hate them" and now I've been on hrt for two years, and I want bigger boobs. ALSO, cup sizes are way smaller than you think they are. the general definition is a letter for every inch in circumference difference between bust and underbust, and if you think about it, A cups are practically nothing. I have C cups (technically) and they're still pretty tiny
Average cup size in the US (natural) is a B cup. There's never any guarantees, but if you're worried and can find a good doctor, I'd talk about it with them to see if there are things you can do to reduce risk (stopping e temporarily might stop growth but idk). Worst case, reductions are an option & have minimal scarring