I see.

HDR depends a lot on the monitor I guess. Mine isn't really brighter in HDR mode than normal because it's an OLED, so the big difference is that the darks can get darker and more detailed as opposed to the brighter brights on HDR LCD/LED panels.

As for VRR, I'm a huge fan of it and I can't recommend it enough. Particularly on high refresh rate monitors and demanding game it's a big win not having to tweak your settings so that the framerate always stays above the monitors specified refresh rate. No tearing. No penalty from not reaching the required framerate. Just a smooth presentation.

You can actually use VRR on X11, but only on for single monitor and it will introduce tearing on the others.