I am on Garuda Linux running their KDE Dr460nized Gaming Edition. It is based on Arch Linux, btw. Because it is Arch, I only recommend it to moderate to advanced linux users, maybe newbies if they are not the kind to go running to a help forum and post, but instead research and figure things out. With that said, Garuda comes with a handy click/install GUI for many things, but a special section for Gamers that makes installing everything you need easy and simple.

If you are a newbie, I would recommend an Ubuntu distro because it has a HUGE help forum to get your feet wet. In that, I would recommend Drauger OS, it is Ubuntu for Gamers.

I guess it depends on what your use case might be. I have heard that Manjaro is decent for a desktop Arch experience, but I have yet to try it.

My use case recently was for a living-room PC that works like a console version of the Steam Deck. For that purpose, ChimeraOS works really well. It's an Arch-based distro that uses the Steam Deck controller-first interface and so far is handling almost everything I've thrown at it. It even has a remote admin app where you can install games from GOG or Epic (although GOG support only installs the base game at the moment, no DLC or updates) or upload console ROMs for emulation.

I would say if you go this route, get a PS4/PS5 controller. The touch space is recognized as a mouse, which removes the need to attach a mouse for those moments when you need to get into the desktop (such as formatting a secondary drive for use in Steam).

Seeing as you're coming from Windows and already have familiarity with Ubuntu, I'd say go with Ubuntu. The difference between Windows and Ubuntu is pretty minimal, and Ubuntu has amazing support because of it's popularity finding an answer to any question is a simple search away. The FPS gains from a leaner distro will be minimal compared to Ubuntu and you still get a fully functioning, well maintained and supported system.

I wouldn't recommend you venture too far from Ubuntu but if you're feeling a bit adventurous, Pop!_OS is based on Ubuntu and is a great option. Any of the Debian based distros would also feel similar to Ubuntu and Windows and will generally offer a user experience that a Linux noob should be able to get into as you gradually get used to using the terminal rather than GUIs.

Damn. How embarrassing. I've notified them.