Question Is 60fps on 120Hz suppose to look worse than 60fps on 60Hz, or is my new monitor busted?

Jun 9, 2021
A week ago I bought Asus vg259q as a new screen for my computer for gaming with Freesync and general stuff (like watching movies).

Whenever I run the screen at higher than 60Hz refresh rates the frame-pacing is all over the place. Tecnically the Freesync works; it chases game's refresh rates at double rate (120Hz for 60fps, 100Hz for 50fps and so on). But it's juddery. Most of my games are locked at 60fps. I'm using GTX 1060 3 GB with the newest Nvidia drivers (the one with Doom Eternal Ray-tracing update). If I limit the game's frame rate with NVCP to 60 Rivatuner shows a flat 16.6ms frametime line but the OSD shows the framerate fluctuating from 100 to 140. Also sometimes the OSD jumps from 120 to 60 as if it can't quite decide which one should it use to display 60 fps.

The things that I've tried are... Vsync on and off ingame, all available Vsync options in NVCP (on, off, fast), frame rate limiter in NVCP (60 and 58 fps). I've also tried disconnecting my second screen that's connected to my mobo. One of the games I've been testing is Genshin Impact which is capped at 60fps and doesn't have an exclusive fullscreen mode so I run it in default borderless and use the "enable G-SYNC for windowed and fullscreen applications" setting in NVCP.

Also if I turn the VRR off and run the display at fixed 120Hz, 60fps looks more juddery than if I lowered the display refresh rate to 60. This happens both on my Windows when the display is connected to GTX 1060 via Displayport cable and in MacOS when the display is connected to motherboard with HDMI and powered with my iGPU.

^^Is this normally suppose to happen? I thought the whole point of high refresh rates was to eliminate these judder problems (my idea was to run the screen in 120Hz in MacOS for best compability for 60, 30 and 24fps material). Or have I missed something crucial here? Or does this sound like a broken monitor that should be swapped?

The processor is 4790K, the Windows is Win 10 2004. Mobo is GB Z97-HD3.