Romance novels are books that anyone can read. The defining feature of Romance is a Happily Ever After; the conflict(s) are resolved and the world is put right again. There's are otherwise few limits, as far as I understand it, and some exceptions I'd still call Romance. A Court of Thorns and Roses (by Maas), for example, is a series with ongoing conflicts across the books. I can count on standalone Romance novels resolving without much uncertainty, at least not in the short term.

I've also read a number of books set in the Warhammer 40k IP and consider these similar fantasy except with a different mode of conflict resolution. If "Romance" is feminine by nature, I venture to consider the books in the Black Library to be "Masculine Romance", with an emphasis on getting what is desired through power over others rather than through power over oneself.

comparing romance novels to 40k is like comparing apples to microwaves.

i also balk at the idea of "masculine romance" requiring over-the-top grimdark violence.