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 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.