is there a good 4k 120hz monitor out there for around 400? gezz
No
With monitors, to get something cheap you have to pick one main thing for the monitor to be good at. The more boxes you want to tick, the higher the price will be. This is especially true when dealing with higher resolutions and refresh rates.
then what the best for wow, 4k or 120hz?
4k.
On average most people sit at 60fps for WoW.
Though you can always pick the middle ground and go with 1440p 144hz or even ultra wide 3440 x 1440 120hz VA monitors which is just a notch below 4k.
Resolution vs. framerate is personal preference, but I lean toward resolution personally. The sharpness it brings is nice, plus it lets you turn off antialiasing because at 4k/5k model edges are smooth enough already. The higher framerate also doesn’t really add much for WoW specifically, that’s generally something you’d want for games like Overwatch and Counterstrike and things like that.