Suggestions for plain romance novels?

Not sure if it's what you are looking for but Devil's Bride is a pretty good period piece. You have to put all your PC expectations away and remember the period is the 1800s (I think, could be the 1700s). I haven't read the others in the series, she wrote stories about different family members. Devil is the duke's name, there's nothing supernatural involved.

Julia Quinn and Eloisa James. Both smart, hilarious, period romance writers. Eloisa James is actually the pen name of a Shakespeare professor -- and lots of literature references show up in her work. I love them both.

I'm almost done with a contemporary called Bittersweet, by Sarina Bowen, that's pretty much exactly the "threat level" you describe. The FMC is a chef looking to open a restaurant in Boston, the MMC is an organic farmer in Vermont. What's between them is distance and nothing else. It's a quick easy read with lots of laughs, although, warning: the sex scenes are pretty truncated, but what's there is explicit. I wouldn't classify it as erotic romance, but it's pretty high heat-level.

I've read the first couple of books in the Warrender Saga (A Song Begins and The Broken Wing) by Mary Burchell, and I think they'd fit your description. Some reviews mention finding them heavy on the music description (they're set in the world of opera), but that's something I liked about them, and I didn't find it excessive. As with MaeZe's suggestion, some of the attitudes on display are very much of their time, but I still go back to them as comfort reads.

Take a look at Harlequin's website--they have descriptions of all their various lines with the types of plots each features. You'll probably be able to find something there.