Face structure - changes a bit on HRT, more noticable in FtM than MtF. MtF may have ffs to alleviate dysphoria and pass
Fat distribution - changes entirely on HRT. Takes about a year to be noticeable and 2 years to be near complete
Hands - change on HRT. Testosterone causes the veins to be larger for trans men and lack of testosterone in trans women diminishes this.
Muscles - another 1-2 year change, but again this does change to be comparable to cis people of the opposite sex
Skin and hair - some of the first majorly noticable changes
Smell - next to bottom growth in trans men, one of the very first changes to happen
The only thing that remains unchanged is the pelvic bone shape and general skeletal structure, but even bone density is a change that happens on HRT.
HRT changes A LOT.
Testosterone and estrogen are the sex hormones, and they’re what causes our secondary sex characteristics. Taking the hormones of the opposite sex will give you the secondary sex characteristics of that sex. Yes, this includes things like muscle mass and smell and body shape.