Some trans people change their sex characteristics, some don't. Some of us quite literally change our sex in a multitude of ways. Some transition just gender. Some transition sex but not gender. And I don't mean just genital surgery. I would argue HRT changes your sex.

And it should be obvious where nonbinary people fit. It's a bimodal spectrum, not two distinct categories separated by a chasm. Most folks lie on either end, but there's plenty of room in the middle.