It became what it is currently the Steam Deck OS or at least the lessons learned were applied to create it. That being said you have distros like Bazzite and Pop OS focused on gaming, you could try those.
I recently deleted my Windows partition and went full Linux for my personal devices. I use Windows for work and it reminds me that I made the right decision.
I use Arch btw
You can set up the boot directly into Big Picture, there are a couple of ways depending on your needs/expectations.
Gamescope did not work for me, I have been gaming exclusively in Linux since proton was published but any time I try to get gamescope working it behaves strangely. I blame my Nvidia card but it’s hard to say.