I can’t speak on multiplayer experiences, but i have several emulators set up on my OLED deck. GameCube, N64, switch, ps2. They work well, and i have a 3DO pro2 i use while it’s docked to my 4k tv, sound through a surround sound bar with woofer - amazing sound. I mostly run skyrim and Balder’s Gate 3 at the moment, but i enjoyed BotW and my son likes sonic.
It’s configured to run at the native resolution of the device, and looks good, but I’m not sure it is really at 4k.
Skyrim performs flawlessly, but Baldur’s Gate gets sbout 15 fps at this rez, so I have to lower the graphics setting. I’m nesr endgame, so there is a lot of city animation.