Trans sports seem the logical answer to me here, if some men who do not class themselves as men do not want to play with men. Its unfair, and unsafe for them to play with women. So..
This would also go for transmen. Though the fairness to men argument doesn't stand at all, in stuff like rugby, I would say its dangerous for a transman to play against a team of men tbh, no matter what their 'testosterone level' is. Some other sports, safety of the transman would not be questioned really, fairness would still be a issue but if they wat to put themselves at a disadvantage, I guess thats up to them.
It would actually be quite interesting in a way, to see which bears out, testosterone level, or male puberty advantage. I suspect the second, but maybe it would be more equal?