So, about the ones I read:
Are You Okay With a Slightly Older Girlfriend? Is great if you're fine with the premise of a 27 years old woman and a 15 years old boy dating, which wasn't a problem for me. The series technically is not concluded from what I heard, bit it reached a good stopping point.
Why Shouldn’t a Detestable Demon Lord Fall in Love?! Is ok if you are looking for something sickening sweet.
Guide to the Perfect Otaku Girlfriend: Roomies and Romance is an ok romance between otaky and gal, nothing particularly special but if you like the genre is a nice read.
Reincarnated as the Piggy Duke: This Time I'm Gonna Tell Her How I Feel! as others starsc isn't 100% romance but is more of your average fantasy isekai. I enjoyed it, although it's brought down a bit by the apparent inability of the author to stick to his ideas until the end.
Endo and Kobayashi Live! The Latest on Tsundere Villainess Lieselotte is a series I appreciate reading and I usually don't read villainess stories. It has a good romance and lots of nice characters. The version currently on sale is the manga, though.