Sorry but I'm confused because isn't RGB-LED is the best possible LED technology, since each pixel is lit individually? What LED tech could be better than that? There are some H-IPS panels with RGB-LED (W2420R, HZ24WD) but (iirc) there is an other one as well which is with a P-IPS panel I just can't remember that one now. Are you saying that those are not full led displays, because I would read the source of that info. I like this subject and I would appreciate the link.
Talking about different IPS types, the quality of the picture is never about the panel only but more about the engineers who design the circuits and the FW (For example there are monitors out there from different brands using the same LG panel what's in the U2311H but all the others got insane amount of input lag and horrible uniformity with the very same panel).
I don't believe in OLED tbh, I prefer the natural "paper-like" look like how a good IPS panel looks, but on the other hand, QLED looks really promising in theory, I just hope my CRT will hold until they arrive