I expect to have a master list of maybe 300-400 films from the five decades consolidated in 4-5 days from now. Once that's in place, you may want to look it over again and see if you find a path through the forest.
I don't think sub-genre is the way to go with this--my sense is that such things are indicative of "copycat" processes that are far more prevalent in latter-day filmmaking than they were in the heyday of classic noir.
But taking the lists and annotating them for sub-genre is useful just to see if that sense is correct. See if you feel inclined to try such an approach.
Additionally, you might simply look at your own list of films in the past decade (2010-19) that you ranked 8 or higher and see if you can put some distance between them in terms of which ones speak to you the most.
Also--is your 8+ rating scarcer than it used to be in previous decades? Would be interesting to track.