For the NTR discussion. I think it all depends on the setup. I consider femdom to be when women exert power and dominance over men. In cases of lesbian NTR, this is far more prevalent because now you have this additional effect of having multiple women exert some kind of mutual and collective sexual power over the MC, on top of now having two women flaunting their own individual power over an MC. It creates an additional element of us vs them, or women vs man, which will indirectly make the MC feel smaller or outnumbered.
I think in some cases, I think NTR with another man can be a form of femdom, if the act is done deliberately to exert power or dominance over the MC, like if a love interest purposely went and got with another men, just to hurt the MC, and in some way, made him an indirect participant(like sending him a picture, forcing him to watch or flaunting the act in his face). If it's just straight up cheating, then it's not really femdom.