Is there a genre or sub-genre for "men's romance?"
Basically a story of a young man solving a business problem while making a few "conquests" along the way- until he finds true love.
Story doesn't seem to fit any of the standard categories.
That's cause it's not a category in a genre; it's general fiction.
There is a category of romance novels that have men as the main characters. Those are called (I think, but if I get this wrong let me know) hero-driven romance.
My most beloved former client Kari Dell wrote two of them. The most recent is Tangled in Texas. Notice the cover is just the cowboy, and while his shirt is unbuttoned, he's not shirtless, nor is he grasping a delightfully disheveled woman to his manly man chest.
If you're having a hard time figuring out category, there's nothing wrong with "commercial fiction."