Unfortunately, without a base level understanding of the entire ecosystem, I stay lost.
my recommendation (as I said elsewhere in this thread, I'm a 10+ year NixOS user) would be to install NixOS on a VM or spare laptop and tinker with configuring it. you can follow the breadcrumbs, for example enabling sshd [0] has a "declared in" link to [1] where you can read the Nix source code of what that NixOS option actually does on your system.
flakes, modules, and overlays are all relatively "advanced" parts of the ecosystem, you don't need to know them as a new user. in particular, you will find many blog posts telling you to use flakes right from the beginning. that's an option, but not at all required.
0: https://search.nixos.org/options?channel=25.11&show=services...
1: https://github.com/NixOS/nixpkgs/blob/nixos-25.11/nixos/modu...
Regarding features: so far for my home setup (few vms on proxmox) I only needed flakes. They age good at organizing multihost config.
But besides it it works smoothly. And I constantly have thought “wait, why we didn’t always do it this way?”
https://shopify.engineering/shipit-presents-how-shopify-uses...
https://www.youtube.com/watch?v=6iVXaqUfHi4
Flakes are a dependency-pinning and hermetic evaluation feature baked into the Nix tool itself.
Overlays are an idiom that uses lazy evaluation to build up larger attribute sets in a modular and composable way (e.g., package collections for a particular programming language).
This was the Nix config that helped it 'click' for me: https://github.com/eh8/chenglab that mentions this guide.
I based my own config off of it https://github.com/richardgill/nix
The arguments probably come from the fact that flakes are 'experimental', but de facto widely used.
I keep checking back every year or so secretly hoping they'll have upgraded the language. It's fascinating how successful Nix is given how utterly opaque the language is.