there is also Heroic, which is similiar to lutris but in my opinion a bit nicer to configure :)

Heroic defaults to an ancient version of Wine-GE. They are currently in the process to migrate to a new tech called umu-launcher which allows them to use Valve's Proton and Proton-GE directly. It's basically done, so should appear in Heroic 2.16 but if one tries Heroic today, the compatibility might be worse than Lutris or Bottles.

I realize I’m probably in the minority here, but do they have an option at the original 1280x800?

Wouldn't it then make more sense to sell you LCD Deck and buy an OLED one? Whether you buy an extra screen or the added cost of a new OLED one, the price difference should be in the same ballpark. Not to mention the risk of damage and the need for a modified BIOS. New warranty on the OLED model would be an added bonus.

It gets ugly really fast.

It's super easy, barely an inconvenience. Just use Distrobox: https://docs.bazzite.gg/Installing_and_Managing_Software/Distrobox/

Games? Nigh impossible.

Decades ago DOS games had custom intro animations but that's not really relevant for current games.