Linux

As others have stated, as long as you are using a distribution with reasonably modern (and maybe frequent) updates of the kernel and mesa stack, it doesn't matter much. The updates of these two packages are what will provide updated hardware support and performance improvements.

Steer clear of Nvidia. It can work on linux, but is a pain due to Nvidia not providing proper open-source driver support. I also highly recommend ensuring you have an intel chip if you need wifi, as realtek and broadcom can be a bit variable in terms of support and stability for wifi.

Wayland is also preferable in my view, due to its significant benefits over X11 - it is more secure, makes your computer much smoother, and supports modern niceties like better multi-monitor support, gestures, lack of tearing, HDR (in the future), etc.

This segues into my next point. It makes more difference what DE you use when gaming - GNOME currently doesn't support VRR on Wayland (appears to be coming in next release at least experimentally), while KDE does. So that is something to think about. I would stick to either of these two DEs as these are the only two that are both user friendly for beginners, and have excellent wayland support. Cinnamon, MATE and XFCE all do not yet support Wayland.

I would steer clear of distributions that are not established, and/or only have very small or single person teams (as this has potential security, stability and support implications) and would recommend Fedora. Fedora has a bleeding edge mesa and kernel (that roll between releases), but stability elsewhere with a solid community behind it and a dedicated security team, built on cutting edge technologies throughout. If you need VRR I would use the Fedora KDE spin. OpenSUSE tumbleweed is also a great choice.

Many users will recommend Arch Linux systems, as this is the hotness, particularly as this is what SteamOS is based on. I wouldn't recommend this even as a very happy Gentoo user, however, as relatively "pure" Arch Linux distributions (and Gentoo), will require you to follow notices on the website, and will require your knowledge and intervention at some point based on this notice; without your intervention, it will likely break your system. So as a beginner I would avoid Arch Linux and Endeavour OS.

Manjaro has had many too issues with the security and stability of their distribution to allow me to comfortably recommend it, and the Nobara and Garuda Linux teams are both too small for me to be comfortable recommending them. Zorin OS, Pop_OS and Linux Mint are all excellent workstation distributions, but their outdated kernels and software (they are based on a long-term support base) mean you may be either giving up some performance or hardware compatibility.