On transracialism: I have looked for explanations for why nobody is allowed to be transrace while transgender is perfectly fine for all. I haven't seen very many, and can only recall two where the answer to someone asking about this wasn't just accusations of transphobia:
The first one was that sex is a real biological concept while race does not exist as a biological concept. Somehow that means the first one is more permeable than the second? In any case, I have read this as one explanation.
The second one was that because of epigenetic inheritance, people of colour have inherited the pain of the brutal treatment of their ancestors in the hands of white slaveowners and/or colonisers, and it is ethically wrong of anyone who is white to transition into the racial group other white people mistreated.
This one might not work as we could equally well speculate that epigenetic inheritance of such pain might be also shared by female people from their mistreated foremothers. But I believe that the real argument here is ethical, i.e., that transitioning into an oppressed race class is morally and ethically wrong and so is not allowed. I'm not sure how transitioning into the more oppressed sex might not also share some of those concerns.
I like a different answer I have read better, and that is that all or almost all people of colour said clearly and strongly NO when they spotted attempts of transracialism.
Women, as a class, however, did not do the same and perhaps would not have been obeyed in any case, because the transgender activism had already created the background for arguing that women, as a class, are privileged when compared to transgender women.