guess i fall in that category (small chested, small frame, small moobs but the tri top doesn't exactly do magic). It does have to do with your frame by the way, to answer your question. you need a binder that sort of gives you a male contour because you probably have no body fat on your ribcage that your chest could "blend in" with.
I'd recommend the 2nd gen. Jersey Mesh from Les Love Boat (or else the Esha extra strength short binder if you can get your hands on it since Love Boat doesn't carry the brand anymore) over the tri top. They only bind where you need them to (these are the shortest two binders I have, so these are the ones with no unnecessary ribcage compression for me, but then again I'm really skinny but I'm like 5'11'' and wear a size small in all my binders (except the tritop which i got in XS and it was still a little on the large side).
I don't recommend T-Kingdom, those just don't bind that well and some people had issues with seams popping after days of wearing them.
