Hey, I think the only way to find out is to try out some different frames. The effect of a pair of frames really depends on your face a lot. A rule of thumb seems to be more squarish frames.
I finally found a pair I liked, but it took a number of "sessions" at the optician. For me, the solution was to simply pick a pair I liked rather than trying to find something that would make my face more masculine. I'm pre-t, and ultimately the glasses will not help me pass at the moment (they're still a "masculine" model I'd say), but they will look good on me both before and after starting t (whenever that will be).