You don't say what else other than gaming you want to do, so it's harder to advise. Still, consider bazzite KDE, easy, stable, relatively close to the bleeding edge without all the cuts, everything you need for gaming in the tin.

Would definitely not recommend KDE Neon. It's more of a showcase of new KDE features than an actual usable OS. I currently use Kubuntu and it's fine. I wish it updated more frequently but the update frequency isn't slow enough to really be a deal breaker.

I disabled snap Firefox, not really because I'm ideologically against snap, but because snap Firefox is annoying to use. Other than that, the OS generally just works out of the box.

I've heard good things about OpenSUSE, but I've never tried it. My personal opinion is that I want to stick to the most common distros so that it's easier to find troubleshooting advice

I use my pc for similar purposes on Linix Mint Debian Edition. Basically mint which is based on Debian instead of Ubuntu. Steam and emulation have been a breeze on it with flatpaks and I've fiddled around with Lutris as well. A lot of features are plug n play in many aspects, but the os gives you enough freedom as to not feel restrictive.

I've found that the community is helpful and big enough to have all my questions answered. You might need to do some tinkering if you use an Nvidia GPU though. I have an all AMD system, and it was relatively easy to get and install graphics drivers, which will probably be your biggest hurdle/headache with other distros outside of PopOS.

I am also gaming a lot and used nvidia in the past and by the description you give I would say openSUSE Tumbleweed is the one. It is rolling release, but they also have extensive QA tests before letting packages get released as updates so it is very stable for a rolling release. And another thing that openSUSE is awesome for is that they have BTRFS snappshotting very nicely configured out of the box so before and after each update it creates a snappshot and if something goes wrong you can just select an old working snappshot from GRUB boot menu. And with Nvidia this breakage was happening well more often the I would like. I also like their Open Build Service where you can find many additional packages which might not be packaged by distro people themselves.

Of course there's the suggestion of installing KDE plasma on PopOS! Which will work quite well but to give some info on the others:

KDE neon is mostly for devs and is less well maintained than other distros. Still definitly not a bad choice.

Tumbleweed stronk. Definitly out of what you say my preference though yes, it's not deb based. You should be able to get what you want though through the app store and the open build service. Really it's discouraged to find random .debs online and install but OpenSUSE runs on .rpm which are fairly commom.

Kubuntu is also good. Last time I checked it's a bit slower moving than pop but that's not inherently bad. Definitly a great "It-just-works" distro. Some people, myself included, dislike snaps which are built in but if you don't know what they are I doubt you'll care. Most of the hate is overblown.

I'd caution against endeavor as it's arch based. It'll demand more from you, stuff will definitly not just work all the time,and if an issue arises it'll be the first to catch it. Like the grub rescue error that showed up about a year or so ago.

Don't use Manjaro. The devs are incompetent and destructive to the ecosystem.

Debian is also chill. There's always unstable (can't remember the current name. Debian Trixie?) For something that's more up to date

Last thing no matter what distro, just like an exe, a .deb is just an archival format like .zip and can be taken apart to be manually installed. I understand not wanting to do this though lol and it's not always that simple

Aside from your preference for debian-based distros, you're describing Garuda pretty well. But the chaotic-AUR is enabled by default, so you'd never need to hunt for .deb files in the first place. And the update script, "garuda-update", has a bunch of nice features by default, like taking snapshots and running grub-update (which would have prevented the grub fiasco that hit the arch-based distros a while back).

The only pain points are 1.) If you don't like Garuda's theming, you'll need to do some minor ricing to start, and 2.) Plasma 6 updates often enough that on a rolling release distro, something minor about your setup might break once every few months, e.g. KDE allows themes to set a minimum taskbar size and all of a sudden your taskbar increases in size, or your wallpaper gets reset for some reason.

I also ran Pop for a couple of years before moving to Bazzite. Bazzite has KDE, Wayland, and can run .deb software through distrobox. It's the best.

i used Tumbleweed. It is great, but you need to configure it for gaming

Just install KDE and see if you like it.