Ok I finally figured out I have a type! I am very weak when it comes to a possessive seme and a strong uke who is also "cool" - smart, capable and could rightly be considered a seme themselves except for their sexual position preference. Bonus points for black haired seme and lighter haired uke (but not essential). Triple bonus points if it has a good dose of tasteful humour, plot and great characterisation!
Some examples of what I really enjoyed are Banana Fish, Yellow, Totally Captivated.

Example of what I'm not looking for is Silver Diamond or Little Butterfly - the uke is too fluffy and everyone loves him and he's sickeningly sweet. I need someone feistier XDD

😎

Fake by Matoh Sanami. The seme is more persistent than outright possessive (though I suppose that is one form of possessiveness), but everything else matches quite well 🙂

Yay thanks! It looks really good. Any other suggestions? 😁

Anything by Ishihara Satoru, particularly Afuresou na Pool, Shounen wa Asu wo Korosu and Yarouze!, though sadly she isn't popular and very few of her titles have been fully scanlated. Most of them aren't really explicit, but since you mentioned SD and BF, I'm guessing you're fine with that.

Also:
Kuchizuke wa Uso no Aji
Moritat
Yondaime Ooyamato Tatsuyuki
Tengoku mo Jigoku mo

😮 Oh my gosh thank you for those recs -- they're all on my reading list now. (explicit is just the icing on the cake; if their relationship is well developed sparks fly with just a touch imho)
Keep these coming