Testosterone is literally a steroid. It's sort of a reductive statement but you don't really think about it often.
It basically acts as a multiplier for the "grow muscle" signals your body can produce.
Men and women can easily have the same outcomes for muscle mass and calorie requirements, but men might not have to work as hard to get there owing to the higher testosterone multiplier on average.
I've also heard that it makes your skin act weird. Several trans people I've talked to have all mentioned that getting their hormones managed made their skin care routine either way easier or harder in a sort of "holy shit" way.


100%! I meant my statement as building on yours, not contradicting. :)
Any time you talk about hormones you have to couch everything in a thick layer of "usually", "often", and "tend". Biology varies a lot, and hormones vary more than most of the stuff.