Hi Robin,
Congratulations on making decisions and getting ready for HRT. I can relate as my particular endo had a two month waiting list but I remained in line because she has a great reputation.
For body shape others will probably come up with a bunch of things I don't think of but my initial thoughts are... it depends.

Cis-gender people have a wide range of appearance based on genetics, age, weight, etc. And I bet you already thought about all that.
A tummy can be difficult to flatten because exercise in that area tends to build muscle and that adds bulk. I think the main thing is watching your weight carefully beforehand and then letting HRT help with shape once you're on it.
I have been self-conscious of my upper arms, I wish mine were thinner. From what I have heard I will just need to be patient and let MTF HRT do its thing over the next year or two.
The thing I have consistently heard, and has worked for me is focus on aerobic exercise and definitely not lifting. I like to run.