i use arch (btw), and i hate how much i depend on the AUR, its very unstable. I switched to flatpak for my gui programs since the cli experience sucks. nix on the other hand works like a native package manager, and thats great for me. but i see that nix also includes stuff like coreutils (because of nixos im guessing). do i install everything with nix? if not what packages do i install with pacman and which with nix?
I think use Nix for as little or as much as you want. I've been using Nix for a long time to get the odd package that isn't available, or that isn't completely up-to-date in the Debian repo. Now that I've learned more about it I'm using it for dev environments and packaging for my software projects, and I'm setting up NixOS and Home Manager on a new laptop.
The low-level packages are there in case you need them. If you install anything that needs coreutils, libc, gtk, whatever Nix will install it automatically. It's all fully isolated from the libraries that Arch installs so there is no need to worry about conflicts. But since Nix packages use only Nix dependencies you can run into some oddities when Nix uses different library versions than the host OS. For example I've had a case where a GTK app didn't match the theme of the rest of my system.