I personally like the "Melo" theme the best, though it seems like releases featuring idol-related concepts have become more frequent lately, perhaps due to their rising popularity. As for other themes, I also enjoyed the ones capturing the atmosphere of a Japanese summer, as well as those that evoke a uniquely eerie mood.
Hm my favorite are NTR, affairs it's always towards these themes that I go to first, then, friends to lovers, friends with benefits to lovers, yandere, Younger but dominant characters and a bit (a lot) of possessiveness xD
I always gravitate toward dark, mature themes like noir, mystery, or yakuza settings with a touch of melancholy. Having a tired, world-weary man with a deep voice show subtle vulnerability and quiet devotion creates an unmatched atmosphere and tension that I just can't resist.