Doctor Daeva for sure is male, Adramahlihk however ... well (s)he could be anything, it's a demon, those might be genderless, or their own separate gender. Or I don't know. Daeva was a real male doctor, who treated an elven girl possessed by Adramahlihk, after a failed exorcism, the demon possessed the only one living being there - the doctor, that's how Daeva became the demon. It's not just a disguise, that Adramahlihk created for himself. I guess Daeva is a final stage of what would become of Lohse, if it came that far, Adramahlihk in full control of the body, able to transform it into his original demonic form.
Isn't that is transgender argument: if female/male/genderless mind in the wrong body she/he/it is trangender person? So if Adramahlihk is female and she in the body of male doctor Daeva, she's trans. The same goes if original gender of demon Adramahlihk is genderless,because body is still clearly males. Which mean that every body possessions where gender of demon/spirit is different from the body which they possess means that they all are transgender people/demons/spirits.