TN, IPS, VA
TN fastest response time, poor color and viewing angles
IPS best color and viewing angles, on high refresh displays, response time is still very good.
VA, good color, often curved display to offset viewing angle issues (but only good for a single user)
These days HDR might be a factor on more premium offerings. Higher HDR number means more brightness/contrast to create better lighting differentiation. Often means backlight zones so the the darks can be dark and the bright parts bright.
G-Sync, FreeSync, G-Sync Compatible
FreeSync Pro, Nvidia Reflex (Requires 30 series graphics card, so you are good there)
OLED still not really a thing yet. And I haven't seen any next gen techs make it into gaming monitors. So some of the...