I started hrt just after my 19th birthday. With regards to the apearance thing... For me, Even with jeans and hoodies, and no makeup, i still looked female after around 6 months... the changes were quite profound and welcomed, though at first, within like 2 months or so, i did look a lot younger lol, like a 16yo boy, then androgynous at 3-4, then female by 6. It wasnt as much the breast growth, but my manerisms coupled with the slim less muscluar frame, facial apearance and hair, hrt did quite a bit to my face... the skin too was nice, but im not sure if it helped as much more than just being really nice now.
I think the first sign of hrt, is possibly muscle loss, and skin before breast GROWTH, first sign is imo nipple change.
The rest; Well, breast growth isnt linked to the others really. Some people will just come out with small breasts... i've seen other girls with broad flaring hips and tiny boobs... its just genetics... then theres my best friend, 30DD with skinny hips... everyone's different. With M2fs, i guess it may have a vague link... age, hrt receptiveness and genetics, but honestly? i'm not 100%