It tends to change your facial features, it sort of makes everything less soft and more angular. I had bigtime babyface too, to the point that when I did pass back then people thought I was a child. It's much better now, although that's partially the face fuzz too.
Here, this isn't the greatest picture example but maybe it'll give you an idea.

That's me pre transition, pre-t, and after being on T for... probably at least six or seven months at that point. I took it for the Trans Day Of Visibility.