I used an MSI Handheld for a bit on the demo stand. It was a piece of shit. It had a higher hz display than the steamdeck but felt awful to hold. Shipped with windows 11 and had no trackpad.
So many of these handhelds have no thought put into them. They are just rushed out to try get some of the steamdeck hype.
Honestly you won’t notice any meaningful performance difference between a “gaming” distro and a normal one.
If you want gaming stuff configured out of the box try popOS. I believe pop also has a custom scheduler and kernel.