Highly recommend Guix, been using it as my daily driver for years now.

System Crafters has a really nice series on getting it setup the way you want it. I think it's fixed a lot of stuff that is a little wonky with Nix -- proper separation of config-time things and build-time things with g-exps, no putzing with bash scripts, grafting so you can reuse builds even when dependencies get updated, and just general good documentation and hackable culture with a pretty active IRC. They've recently added support for also managing your dotfiles the same way you do packages and system config (Guix Home). They've also pushed the boundaries of bootstrappability/reproducible builds so far that bitcoin-core is now building on Guix for security.

The system is pretty well thought through, and has saved me a few times where I would've bricked my machine on a mutable distro -- now, I can just boot to a previous version of the system from the bootloader whenever my lastest changes are messed up.