Questions about the Valars’ gender

I’m currently re-reading The Silmarillion and I have some questions regarding to the origins of the Valars’ gender after reading this excerpt:

”When they desire to clothe themselves the Valar take upon them forms some as of male and some as of female; for that difference of temper they had even from their beginning, and it is but bodied forth in the choice of each, not made by the choice”

If this excerpt means that the result of the Valar being male or female is based on their natural temper and personality traits, does that mean they have no gender/biological sex before they enter Arda? So plenty of gender studies believe that biological sex has been heavily affecting one’s gender identity/roles. So does it happen in the other way for the Valar, that their gender traits (the features that make them more masculine or feminine) affects their ultimate sex?

Secondly, if it is true that they have no genders in the very beginning, would this setting become paradoxical with the origins of Melkor and Manwe, because Melkor and Manwe have been long before referred as a “he”, and it is stated already they are twin brothers before Arda is even created. Ulmo and Aule are too already referred as males before they enter Arda.

Maybe I miss something when I was reading this part. For the involvement of gender studies, I’m currently studying a course related to gender and that’s why this question comes to me when I read The Silmarillion. I known it’s fiction and gender issues is never the point of the story, but it makes me wonder more about the relations of gender and sex in real life. I hope someone could give me some answers regarding to this questions.