I am 64 and have experienced remarkable changes. I have more than adequate boobs, an ample round butt and very smooth, soft skin. My face has changed a lot too. I've been on HRT for six years. The rate of change seemed to accelerate in the last year of two.
Nothing much happens for 6 months or so. It also takes time to see the end result. Consider this: It takes roughly from age 12 to 22 for natal born girls to complete puberty. A 16 year old is nowhere near complete.
Of course bone structure doesn't change, and a bald head won't grow hair. Your genitals will probably shrink quite a bit, and erections will be gone eventually. Mine have reverted to about what I had at age 10.
There are several advantages that accrue to the older transwoman. You naturally have less testosterone, so you don't have to fight that. If you have much fat, you will have an enzyme called aromatase that converts testosterone to estradiol. Lower testosterone, higher estrogen, and the feminization process has already begun. You've got a head start.
The physical differences between man and women naturally lessen as we age. Men become more feminine, and women become more masculine. You may never look like a beautiful 20 year old girl, but you could more easily look like an average 40 year old woman. You will definitely look younger after a few years of HRT.
HRT works, but it takes time. I am amused by the tales I sometimes see in these forums. "I've been on HRT for four days and have a C cup!". That doesn't happen.
Randi