Has anyone used AtlasOS?

I generally would recommend staying away from third party modified versions of Windows. This would be especially true for OP as you seem to be a relatively inexperienced user.
Usually the security risk isnt worth whatever they offer and most of the time any features they offer could usually be accomplished within standard Windows.
- I heard (back when it was featured on Linus tech tips), that it completely disabled Windows defender. Big red flag IMO.
  
  It's optional

AtlasOS in a windows spin that's just straight up insecure and borderline broken given how many tweaks it makes and it disabling updating
Examples of cringe :
https://github.com/Atlas-OS/Atlas/blob/main/src/playbook/Configuration/tweaks/qol/startup-shutdown/force-end-shutdown-apps.yml
Hope you saved your word docs, because this insta force kills any app on shutdown
Hard drive full? you'll never know
https://github.com/Atlas-OS/Atlas/blob/main/src/playbook/Configuration/tweaks/qol/shell/disable-low-disk-warning.yml
- Yikes, thanks!

it is litterallyjust a windows debloater script, I used to use it before I went linux

This is really cool and I'm glad it exists for those stuck on Windows for certain games. That said, I'd still highly encourage anyone interested to give Linux a shot. I ran it as my daily driver for years about a decade ago, but finally switched back to Windows because I was spending too much time trying to get my games to work. I finally got fed up with Windows 11 and moved back last year. Holy hell has gaming on Linux come a long way with Proton. Everything I've thrown at it has worked flawlessly, and runs at least as fast as they did on Windows.
That said, I get that not everyone wants such a paradigm shift or to learn a new tech just to play their games. In the interim of not running Linux on my desktop, I still worked with Linux servers and used the Windows Linux Subsystem, so I get that I'm a little biased in how easy the switch was. You can find distros that are very beginner-friendly, however, or even specifically gaming-oriented.
But yeah, for those stuck on Windows due to games with pervasive anti-cheat or whatever, I get that AtlasOS could be a gamechanger.
Thank you for coming to me Ted Talk.
- I admin linux systems all day at work, and in my spare time on my home lab rackmount setup that lives in the spare bathroom, and I say that to make clear that I'm extremely comfortable with Linux. I got a gaming laptop recently and loaded Ubuntu onto it, and was very underwhelmed with the gaming performance on it. My SteamDeck ran many of the games better, and there were a bunch issues with the OS not being able to keep the integrated graphics card vs the discrete one straight (e.g. switching the load order on reboot, making games constantly try to run on the integrated card), that just made me eventually give up and put Win11 on it. At this point, I'd love for Valve to release a "SteamLap" gaming system, because clearly Linux needs that tight control over the hardware config to get games working well.
  
  Well that's unfortunate. I guess different hardware and configs can really make all the difference. In my case I'm using a desktop with no integrated graphics at all, so no chance of that particular problem happening. This build is all-AMD and using Wayland.
  I've only had two small issues thus far, across the dozen or so games I've tried on this setup. Both were very easy to fix, though one is worth mentioning as it's loosely similar to yours: in Valheim literally every time I started the game it'd default to the wrong audio output and I'd have to manually switch it back.
  Sorry to hear about your own bad experience. Given the rate at which the desktop ecosystem keeps improving, however, and marketshare creeps up, I'm sure in a few more years it might be worth giving it another shot with your setup.
- I had a very similar experience but just kinda glumly stuck with the broken experience in that in between, and just played what I could get to work. But now with proton, specifically the ge version, there's isn't a game that I can't play (that I have wanted to play). It's pretty amazing how quickly the changes and improvements to gaming on Linux have come.
  I also have an AMD system now, which might be a big part of why it's so painless now.
  
  Yeah, I think AMD makes a huge difference there. My old Nvidia card had all sorts of issues with screen tearing, but my current rig worked flawlessly under Wayland with no tweaking necessary.

You can build a recovery disc/thumb drive from within Windows.
And if backing up is a pain, what do you do if your machine dies? You should already have a backup.
- That's been looming over my head, yeah... So then, EasUS Todo Backup? Seems to tick more boxes than any other on: How to Make a Full System Image Backup in Windows

I have AtlasOS. I only use Windows for two games, Rust and Destiny 2, that absolutely do not play on Linux. You will absolutely get better performance because the number of background tasks running all the time is quite minimal - it's clean and there's no store, no crappy apps you don't want. I don't care about security on the machine because I literally only game on it and maybe a little bit of web research if I get stuck on a game somehow. Anyway, I think it's good, it's really how Windows should be - if Windows didn't get so bad perhaps I wouldn't have gone to Linux.
You could try dual-booting for a bit to see how you like it.

To my knowledge they did some horrible "performance" fixes like disabling Windows Defender.
Windows requires you to install random software. If you are really careful, you could live without antivirus, but honestly just dont.
If your PC doesnt tolerate the overcomplicated Windows 11, any Linux distro is lighter.
I recommend to give Fedora Kinoite a shot. It is a very modern distribution model.
Fedora Discussion is a good resource for help, and I am always down to fix the small Kinoite issues like video codecs or flatpaks.
- By default defender is active on AtlasOS. You can disable it manually with bat script
  
  Okay then that was the "extreme" mode and maybe was already removed.

I've used it for VR, which is the only thing I keep Windows for. It's pretty good however I'd say having experience with Linux is a good idea, I definitely wouldn't treat it as a drop-in silver bullet for Windows minimalism (if such a thing exists).
By the sounds of it you're inexperienced with OS-hopping, so if you're going to start looking for things like this just do it properly and give Linux a go. You'll learn so much more and get a much nicer experience at the end, then if you decide you still need Windows then go and use someone else's computer to make a USB. I wouldn't bother trying to make one on Linux, it hardly ever works in my experience.
For clarity, I now just debloat vanilla Windows 11 with Chris Titus' tool. Still only used for VR and Game Dev.
If you go with Atlas, just know you're putting your whole system into the hands of a team smaller than most Linux distros that's doing more work than all of them, so I doubt Atlas is going to be around for much longer. Whereas something like Debian, Mint or Pop! is here to stay.
There's also far less chance of your system breaking if you go with Linux. Really in this situation there is absolutely zero reason to not go the extra mile and hop to desktop freedom.
- Correct, Oracle VirtualBox was the furthest I went. It was interesting, but:
  there is absolutely zero reason to not go the extra mile and hop to desktop freedom.
  My digital life, in both professional and personal capacities, is intertwined with hundreds of my AutoHotkey scripts, which appears to be Win-only; AutoKey is the closest thing that I could find and is so much harder to use or even understand.
  Anyway, thanks for that Titus utility!
  
  Chris Titus has excellent tutorials/tips on how to keep Windows from being Windows, check out his Youtube (Piped).

FOSS Windows cant be. Though would not trust custom isos.

I’m using it for 2 years. Nothing bad so far.

I probably would have if I had heard about it before I reformatted last (it wasn't that long ago). I didn't feel like re-installing again so soon. I have it bookmarked for later though.

- Never heard of it; thanks for the tip!

Why is this in free and open source software? Last time I checked windows was proprietary
- True... forgot! I wanna move to Linux but I'm having trouble with Python (to port over my Windows-only AutoHotkey scripts)...
  
  For once that actually sounds like something you could use AI for and it would be useful