I am also thinking about making my own image based on silverblue. there is a video made by bigpod a youtuber about how to make your own custom ublue image
Personally, as a gamer, I use Bazzite, but recently I’ve rebased to a fork of it with my own customisations, and it’s been amazing.
Distrobox > Toolbox btw. Both use podman behind the scenes but Distrobox is a bit more easier to use/fleshed out for desktop usage (eg makes it easy to export/integrate container apps with your the host).
I’d also recommend checking out Nix for installing any packages not on Flatpak or your Distrobox distro, as Nix has its own advantages since it’s you’re running real application binaries directly on your host OS, instead of an exported script (as in the case of Distrobox), so you get better/direct access to system resources and won’t face some of the quirks/bugs you may get from running a containerised app.