Skill issue. You probably held your keyboard wrong or something. Simple xrandr commands work fine like they have for decades. (Of course if you've moved to Wayland then who knows).
Traditionally it's used to launch a full-screen application, usually a game, but you can launch your window manager through it, if you want your desktop session to use a custom resolution with custom scaling and/or letterboxing.
CUDA, and ray tracing performance.
I get it, I've heard the same from the sway maintainer, maintaining their crusade against Nvidia for a couple years now (the --unsupported-gpu flag used to be something like --my-next-gpu-will-be-amd), with some good arguments about how anti-foss Nvidia is. And if that's how sway wants to be then that's how sway's gonna be.
But with steamdeck and now steam os showing better performance than windows on handheld gaming devices, and with people getting more and more annoyed with Microsoft's bullshit in windows (like unwanted AI integrations), I think all of us Linux enthusiasts have a really good opportunity here to pull a huge influx of people in, if we're willing to budge just a bit on some of our dogmatic crusades against companies like Nvidia.
There's more Nvidia cards in the wild than AMD, according to steam surveys by a huge margin. If we can get Wayland display managers working well on Nvidia thenthat's a lot of new people we can bring into the fold!