krn In my opinion passability depends on you. If you have money you can be passable at any age. But you have to work hard for it. If you want to see transformations of transwomen, you can search it on reddit. What one needs to be passable as woman:-
Most important is voice, it plays important role in differentiation of gender, this is where most transwomen suffer.
Then comes face, many transwomen get good results in facial features just by hrt, one can go for facial surgery if not satisfied.
Body is important too. You need good fat distribution to appear like a woman, hormone treatment and exercise helps one get in good figure.
Dressing and hair styles. HRT is a long process so one must know which dress or hairstyle is feminine enough for her current phase.
Behavior, body language, confidence. One needs to work on these three things to be attractive as a woman. The way one speak, they way one treat people must be very feminine.
All these goals are achievable. But one needs to be very strong and positive and confident. Because HRT plays with mind, and we are never satisfied. Sometime I cried to be passable soon, Now i cry to be beautiful enough . But now the life is very beautiful, that struggle worth it. I hope it helps you and I'm not missing any point.