When did you try Debian? Nvidia should be quite painless since they added the official non free repo. But make sure to install a backports version of the kernel and firmware. And modern apps should be installed with flatpak.
Anyway. I suggest that you try Debian again. There is nothing better out there.
I believe Guix System (or all Nix/Guix derivates) is the closest one. Otherwise I would say Yocto (not really a distro), Gentoo and all the container based distos (like openSUSE Micro).
Yeah, I meant Scheme as you’ve already figured out.
I would say that nonguix makes nonfree stuff trivial: https://gitlab.com/nonguix/nonguix
However, I do advocate that Guix introduce an official “curated” nonfree repository (like Debian). I believe that would make more good for user freedom and reproducibility. Almost no mainstream hardware works well with the libre kernel.
Nah. GNU Guix System. Or Debian + Guix.
Nix has more packages but Guix is much more well documented and coherent (anecdotal and subjective). Also nice with scheme instead of yet another DSL.
If one wants rolling, I would suggest NixOS, Guix System or Tumbleweed. Or something container based like Silverblue or openSUSE micro.
But rolling doesn’t really make sense. Just go with Debian/Leap and then use Flatpak, podman, Nix and/or Guix on top of that. For Desktop.