I haven't played much beyond 4K resolution but it works and works well.
The LG UltraFine is not a hardcore dedicated gaming monitor (eg not 144hz and I couldn't tell you what ms the response time is), but I am not a competitive gamer and honestly 60hz/60fps @ 4K is absolutely gorgeous to my eyes and I am not wanting for more.
The two paths for 10bit 6k60 are either HBR2 + DSC, or 2x HBR3 streams. The 2x HBR3 streams have several gotchas - not daisy-chainable, limits the XDR USB-C ports to 2.0 speeds, requires a TB3 controller with 2 displayport inputs, and I'm not certain it even works with non-Apple TB3 firmware.
So I just run a short DP1.2 cable from the Nvidia card output to the DP1.2 input on the motherboard, then plug my LG monitor into the Thunderbolt 3 output on the motherboard, and it all works like magic.
I'm assuming it would work exactly the same way on the Pro Display XDR. The only caveat is that I think this setup is limited to 4K. I didn't dig too deeply since there's not enough of a difference between 4K and 5K IMHO to make the effort worthwhile. 6K might be worth figuring it out though :)
I upgraded to a LG 5K (same DPI, 27", 5120x2880) with the gc-titan-ridge thunderbolt card, but that was sort of a pain on an unsupported machine so I am moving to a M1 Mac mini + Thunderbolt PC. Hoping to drive it with a 3080, but I think it should be fine.
For any fast paced competitive games, you should be able to drive 60fps with the right hardware, but at the same time you will be held back by the lack of a greater than 60hz refresh rate.
I honestly can’t go back to a lower DPI; it’s so much easier to read text compared to lower res monitors.