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. 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.