If you’re looking to get started with nix-darwin, @ryan4yin has an excellent kickstart repository! Check it out here. Additionally, the official nix-darwin repository provides a comprehensive guide, especially useful for your first iteration and switch.
You can safely customize almost every setting on your macOS with nix-darwin. For more details, take a look at my System Settings configuration.
No worries! nix-darwin integrates seamlessly with Homebrew, allowing you to install any Brew or App Store application you need. For more information on how to do this, see my Homebrew and AppStore configuration.