I'm probably gender apathetic, so I don't really care if a PC is male/female. My issue with some characters is their actions. If a character is dumb, or pointlessly deceitful? That's going to create a big disconnect for me. Same thing if they are an ugly bastard, since I don't really want to see that having sex with someone.
Every VN i play i use my alternate ego "Jake". He likes alot of taboo acts, basically what i might do if i said "fuck it..." lets live life like i have a week left to live and dont give a shit about anybody else or who i hurt.
Harems, impregnation, corruption of young girls, incest, rape, are all on the table and preferred in the AVNs. But i must also say that ive played a few AVNs that were well written and more about love and relationships that i did enjoy, although those are rare.
With that said i have a certain dislike of games that force anal/blowjobs on a girl or some gay bullshit, when there's a perfectly ready cunt i could fill. edit - oh and i should add Cucking... If the MC gets cucked without extreme revenge possible, that'll be a hard (but going limp) and fast uninstall...
I found it super hard to play a game with a female protagonist, i don't put myself in the place of the MC but the ideia of being a male and acting as one is more appealing to me.
Things like dom or sub don't bother me, i'm down for anything