Flannel was also a mainstay of butch lesbian fashion for a long time. So it really depends what kind of look you are going for, but it certainly does not accentuate curves in my own experience.

Many crossdressers use “breast forms”, fake silicone breasts that one be worn with a bra. Some come as a “bra”, of sorts. It may be worth looking into for you. AFAIK it is recommended to not go for the cheapest ones though, because cheap silicone can be smelly and/or uncomfortable to wear.

It is perfectly valid to reject your gender. You can decide what that makes you, friend. 🙂