Removing / disabling useless services, tweaking registry…

That’s the opposite of comparable since none of that was done on Steam OS.

I’ve seen a couple on Linux, though I don’t remember their name rn.

“Gaming Focused” distros aren’t anything special outside of having some pre-installed software.

Something like Ubuntu or Mint, which would be more comparable to a desktop experience like windows, ready for productivity

SteamOS has all of those same productivity tools but I’m not sure how that’s relevant to performance.