heres a rule of thumb for headcanons: dont take away already existing representation.

if a character is canonically a lesbian, don’t go “but what if she was bi?”

if a character is canonically a transboy, don’t go “but what if he was genderfluid?”

theres a multitude of straight and cis characters you can headcanon as whatever the hell you want to. leave the characters that already are canonically part of a marginalized group alone.