The Switch is more than proof enough that pretty much any modern game engine can compile to an ARM target with zero issues (though Nvidia’s low level APIs help, not sure about Qualcomm).
But there’s zero chance older PC games would ever be updated, and by older I don’t mean ancient, some AAA studios stop issuing updates in about one year after release.
So it all comes down to being able to emulate X86 on ARM… The best example we have is Apple, and games run but with a massive performance hit. Microsoft’s implementation is borderline unusable. I’m not sure what to expect from Valve.
I can’t test it (not colorblind) but many recent developments have been made with Microsoft’s help, and for all their faults, Microsoft is usually quite good with accessibility so perhaps it’s the good version.