Testosterone and estrogen levels definitely influence facial femininity and masculinity, respectively. The more T you have floating around, the less fat deposits you'll develop in certain areas of your face, whereas E will soften your face by repositioning some of your body fat in your face in ways that we associate with being more feminine. At least, that's what I've come to understand. In any case, I guarantee that skin softening is not the only influence on HRT feminisation.
Congrats on nearly turning 18, and good luck on HRT!