I've had this on my M2 Air for a few days now, and done a bit of messing about.

From my somewhat amateur perspective, while it's cool that I can boot up SteamOS, Crossover + NotProton + macOS Steam has proven to be more useful.

While I could never hope to actually play it in any useful way, I can get Horizon Forbidden West to launch with Crossover. It's 15fps on low settings while standing still, but it launches. In SteamOS I can't even get it to launch. Alan Wake Remastered runs very well using Crossover, while the original Alan Wake does run, but has an unplayable amount of frame lag. In SteamOS, AW Remastered won't launch at all, while AW OG runs really well. Also, the original Talos Principle ran really nicely under SteamOS. I've not yet tried it using Crossover, but I've no reason to believe it won't also run well.

So at the moment my view is that FX Steam Launcher is very cool, and I'm looking forward to seeing what comes of it, but it's very much at beta level.