Hi Jenny,
Whatever choices you end up making, you've done well to find this place. I started transition with HRT about a month before my 21st birthday, and I can tell you from experience that it's certainly not too late. Some things, like the skeleton, will never change (except for maybe a little decrease in height due to the decrease in muscle mass), but the long-term effects of a testosterone-based system can be largely avoided. I hope you stick around, ask questions, and get the answers you need.
Lia