It doesn't work. The OP never tested if it works past 120hz before posting that thread. If you set 144hz + VRR using the widget hack, it says it's in VRR mode but refresh is static at 144hz.
Even when the VRR mode is working, it's plagued by very poor pixel response times. The monitor is locked "normal" overdrive in VRR mode which gives you >>10ms transitions on most G2G. The average 9.1ms is misleading because it's being pulled down by grey to black transitions.
The XV273K is constantly on sale for a reason. Just get a good 1440p monitor if you're only willing to spend that much.