I had top surgery before T and I didn't have any issues with it. I went to Garramone and he did require a letter but that wasn't hard to get. I had surgery in January of this year and started T two months ago.
As far as the chest growing back..seems unlikely as they pull all the breast tissue out. (or should for double incision)
I don't think my chest was bad even though I never bulked up before hand/wasn't on T. I guess it could be better if I had some pecs just for the placing of the scars I guess? but scars were not a concern of mine.

this was three weeks post op/no T

five months post op/two weeks on T

seven months post op/two months and two weeks on T
The scar on my right side is doing weird things because of the way that I had my arms...usually looks like the other one.