Congrats on the prescription

The thing with transition, is that with the exception of voice changes for FTM's age is a reaaaaaaaaaaally rubbish predictor for anything on HRT. Obviously the younger you are the better your results will be across all development, but even looking through the forums it becomes quite clear that a number of older women (50+) grow into themselves to become really quite beautiful inside and out

...considering that you are not overweight, and kinda pass already, at least in your profile pic (I have no clue about in person) you are probably better positioned than a lot of younger girls to take advantage of the E!!
Also on the progesterone thing, from what Ive been told it won't necessarily accelerate growth, or even change the way your breasts look, but it will develop the internal structures (milk ducts and stuff), which is incredibly important if you want to breastfeed (I don't know how relevant that is for you)
If I'm completely wrong, on all this (which is a distinct possibility) some other lovely people can probably give you a better idea than me

Good luck!!!!!