Transfem here, on estrogen monotherapy since early 2021. Super low T level; average or above estradiol. I do take a DHT blocker (finasteride). Added progesterone 2 months ago.
This is all very much YMMV.
What I can almost guarantee unless you have a very unusual endocrine system, are softer skin and breast growth. You'll notice sore nips in a month or so, then thinner/softer skin after 6mo to a year (it's constant but takes a while to appreciate).
HRT has not prevented me gaining or maintaining muscle. I was skinny and not super strong before, but the physical nature of my warehouse job has actually built muscle. My glutes and thighs are like steel. Added bonus, upper body strength has increased and rounded out my breast size <3 highly recommend staying fit while transitioning.
I don't weightlift, I just lift a lot of things, move constantly... and work my ass off. Ultimately I think it will come down to "use it or lose it". Same with the noodle. It will absolutely atrophy if you don't actively use it.
Fat redistribution... not really seen this. Altho I'm skinny so that may play a role. It's very very subtle if anything has changed shrugs probably most overrated and underwhelming aspect of HRT for me personally.
Testicles have shrunk noticeably. Makes sense as they are literally useless now xD mine aren't super tiny, they still get in the way and hurt. It's easier to tuck when they shrink, a lot of times they find their way up there naturally. Getting them snipped ASAP.
any other questions, ask away <3