There's two things to consider: higher framerates and variable framerate.I must give back my gamer card here. I’m afraid that I just don’t get gsync, or hdr for that matter. I suppose I need a point of reference when all I can obviously get is one version running at a time.
Do what I play feels good to play, or is the IQ to my liking or not, that I can get. But I lack the expertise to imagine what it would feel like in another setting, so to speak.
I should maybe try to play a locked 30fps game.
You didn't mention higher framerate, so I assume you know how much more fluid 144 FPS can be over 60.
The next problem is hitting the framerate of your monitor constantly. Even with vsync, you will have cases in games where you can't hit that. You will experience stutter. Maybe you are so used to this that you don't notice it, but it's there. Variable refresh rate allows you to just fix this. When I'm playing game, say Horizon, it can go from 80 to 90 FPS, and I don't see the game stutter, it just updates the screen a bit faster. If the game wildly fluctuates from say 30 to 120 (to give an extreme example) it will still look and feel very jarring, but for the more gradual variation you experience in games, it will just be imperceptible.