This is a great time to try!

Personally, I was in the same boat. I have landed on Pop! OS for my daily driver: https://pop.system76.com/

I dealt with Ubuntu, trying to get NVIdia drivers to work, no native flatpak, etc etc. PopOS has an NVidia version with the drivers baked in already, and apps just... work. It has been the lowest annoyance distro I've ever used, and I can't recommend it enough.

(I do gaming, AI stuff, coding, pretty much anything I've had to do Pop! has done a great job)

Linux Mint if you want a "just works" distro that isn't Ubuntu. It's Ubuntu-based, but with a better desktop and no snap.

Nobara if you want a distro that focuses on gaming. It's Fedora-based and maintained by Glorious Eggroll, known for his custom Wine and Proton forks.

If you want Arch, just use Arch. It's much less of a bitch to install with the archinstall script compared to earlier releases. EndeavourOS is another option -- basically Arch, but preconfigured with a desktop and a graphical installer.

I highly recommend Linux Mint, foe the most important reasons:

• The Driver manager allows you to install any non-libre drivers you're missing from the internet

• Comes with Flatpak already set up

• It counts with LiveCD(Like Ubuntu) to test the distro before installing it, you want to spend some time here before you fully commit

Also, watch this video before switching to Linux, it's the most honest.

https://www.youtube.com/watch?v=fvkc5WzciHw

I don't game much but I'd try to stay closer to the debian ecosystem, or one of the more well-known distros. There are a lot of cases where there's a debian and ubuntu installer for something and otherwise you gotta compile or hope for an appimage or flatpak. Ubuntu's out because snaps are horrible, although you can get rid of those. Personally I install debian on all my boxes. It's a really minimal distro and things tend to go pretty fast because of that. Debian or I hear Fedora's great.

I'd go with Arch, or EndeavourOS if installing Arch isn't your idea of fun.
It gets the newest drivers first and the AUR includes basically every software available for Linux.
Go with KDE, since it's much saner than Gnome, and use the proprietary nVidia drivers. Anything else will limit your performance.

Don't worry about sudden breakage, that's a thing of the past. A good practice is to put the following in your .bashrc:
alias update="yay -Pw ; sudo pacman -Syu ; yay -Syu ; sudo find /etc -name *.pac*"
then use the update command to update. yay -Pw shows all new items in the Arch news since your last update. A couple times a year there are messages about updates requiring manual intervention in there.
sudo pacman -Syu ; yay -Syu updates the Arch packages first, then the AUR packages. Seperating these is good in case there are dependency issues. That way, your base system still updates fine, even if the dependencies of an AUR package are out of sync. (This never happened to me in 10 years, but I do it out of principle)
sudo find /etc -name *.pac* lists all config files where there's a new version available, but your old config wasn't overwritten cause you've changed that manually.
(You can get even more fancy with updating your mirrorlist first, always checking for keyring updates first, checking for orphaned or abandoned packages, etc. but lastly, system maintenance can never be fully automated)
(If this seems too complicated, you'll be happier with a different distro)

Fedora KDE spin. Should be similar to your Steam Deck desktop mode and it is most likely to land KDE 6.1 very soon, which improves the Nvidia experience a lot due to explicit sync.

I think the RPM Fusion repo for the nvidia drivers is enabled by default so that you can easily install them.

I need some advice on what to throw on this laptop - and some suggestions on how to squeeze the best performance out of this (Optimus vs. Proprietary NVIDIA vs. Open source drivers).

One thing here, the open source Nvidia drivers still have a lot of performance issues. It's only fairly recently that NVIDIA has opened their drivers up enough to allow any kind of reasonable performance from open source drivers, and getting them up to par is still a work in progress. So stick with the propietary drivers for now, but keep an eye on the new open source driver, NVK.

(As far as distro recs go, I recently started using OpenSUSE Tumbleweed and am really liking it, but I don't have enough experience with it yet to make an informed recommendation)

Since you have Nvidia you'll want to use the Nvidia proprietary drivers for the best performance. The open source driver for Nvidia (nouveau) is awful when it comes to gaming performance, unfortunately. (Although this will soon be fixed with NVK)

Depending on your distro of choice, you'll need to figure out whether you want Secure Boot on or not. I believe Windows 10 doesn't require Secure Boot to be enabled, but I think Windows 11 does. So depending on how frequent you want to be booting into Windows this might be a bit of an annoyance. You can leave Secure Boot disabled and use the Nvidia Proprietary drivers as-is, but if you want to enable Secure Boot you'll have to sign the Kernel yourself - it's a pretty straight forward process.

I recommend you try to keep Secure Boot enabled for the added benefit of security and ease of use when dual-booting, but if you don't want to go through the hassle of signing your own Kernel, then simply leaving Secure Boot disabled when in Linux will suffice.

I recommend against using Ubuntu because of Canonical's many poor decisions with Ubuntu. I won't get into it right now, but if you're comfortable with Ubuntu don't let me stop you from using it.

In reality, you can use whatever distro you want. One distro isn't inherently better at gaming then another. It's a matter of configuration.

Just stick with what you know. So either Arch or Ubuntu. Maybe Pop if you want something a little bit more gaming focused. But I guess out of those Arch should be the best since it will always come with the latest packages, especially for your nvidia card, which is finally moving towards better Wayland and later open source support.

Honestly, it doesn't really matter, pick the one you're most familiar with. Performance-wise, distros are largely the same, unless the distro ships really old libraries or something.

So I recommend either Debian or Arch since that's what you're familiar with.

If you want to try something new, consider openSUSE MicroOS. It has a readonly root like Steam Deck, and you interact with it in transactions, so you get a really solid system. Theoretically. I haven't actually used it, but I do plan to once I need ti reinstall one of my Tumbleweed systems (or maybe I'll reinstall my Leap NAS at some point).

And yeah, avoid the nvidia open source drivers. It's a cool project, but performance sucks because nvidia refuses to provide technical documentation.

SteamOS is based on Arch, if you want a similar experience you can either install Arch or any others Arch-based distros.