I've used *nix extensively headless for the last 30 years, but I have decision paralysis when it comes to figuring out what the heck Linux distro is good for a desktop.
As for distros, pick something established that looks good to you. You said you have experience, so you probably know what you want from a distro. I ran arch on my machine a lot but recently switched to fedora for its simpler installation.
As for the scaling, I use it on a 1080PC laptop screen but also sometimes my 3440x1440 display and haven't really run into bad scaling. Were you using X11 or Wayland? I've been on Wayland for years.
Ideally you'd spend at least a day or so trying them all, and about a week reading and watching about their differences, pros and cons.
Unless you are using nVidia for gaming or have an obscure hardware configuration, chances are you're supported wonderfully well at this very moment, by at least 2-3 distributions (Mint, Manjaro, Fedora, Ubuntu, Bazzite, SteamOS, PopOS, CachyOS -- you'll also have a choice KDE/Gnome).
All you need is pendrive. For the super easy transition you'd want an entirely separate system drive (nvme for example). I know, its expensive. I said for the super easy transition, its not necessary. Slow portable disk to store your current documents and game saves should be enough.
We live in the exciting times.