Yep. LG people can be biphobic and transphobic. Gayness doesn't erase someone's ability to be a bigot. It's inherently transphobic and biphobic to assume a hetero-appearing relationship is hetero and it's dangerous since a lot of trans people want to keep their identity safe. Sucks, right?
Cheating is really simple. Person A sleeps with, or engages in romantic/emotional relations, with Person C, without telling Person B and without Person B's consent. Polyamory isn't really any different. If someone in a poly relationship is doing something without telling their partner(s), getting their partner(s)'s consent and they are intentionally hiding it, lying, etc they are probably cheating. The entire point of polyamory is being open, communicating and discussing what is and isn't okay. If Person A and B have discussed them sleeping with Person C, and everyone consents, it's not cheating.
That chart is incredibly interesting. I didn't know it could get so complex.