Yes, all packages in nixos are available as binaries to download.
The comparison with Arch was just in terms of number of packages. Not the binary availability.
At the bottom of this page, they say that binary cache is currently at 120TB. https://nixos.org/community/index.html
If packages being available as binaries is the main criteria, nix has you covered there.
The biggest issue for most people with Nixos is the learning curve just because it’s so different.
If you have Costco membership, their optical department is pretty affordable. Frames are $50-80. Lenses another $80 or so, but depends on complexity and of you get transitions and whatnot.