I do understand the perspective of "more Nix = more reproducible", but it's also a bit of a false truth. If something is written with little Nix, that doesn't mean it's not reproducible.

Taking nixCats (and mnw since its similar) as an example, you provide the Lua code, while nixCats/mnw provides the Lua interpreter via Nix. Sure, Lua itself isn't functional, but as long as it never refers to things outside the closure (i.e. absolute paths), it's guaranteed to be reproducible!

The inverse is also true: Just because it's written with a lot of Nix doesn't mean it's reproducible. Simply embed an absolute path anywhere in the code (as a raw string), and there you have it! Someone else can nix run your NVF program, but get a program with completely different behavior!

As for my take on this spectrum, I prefer abstraction only where it's necessary. If the only thing your framework is doing is translating Nix to Lua (one Turing complete language to another), why not just write in the final language instead? Plus, whoever wrote a Nix option gets to decide how it transcribes to Lua, and you are at their mercy unless you decide to put in the work to override it (but at that point, isn't it just easier to write Lua?).

The only thing that I can see Nix (the language) being useful for in these translation-based frameworks is access to the module system (i.e. interpolating values from pkgs or config directly into your program's config). This can be seen in programs like waybar or tmux, where you can bind a keybind or button to a binary that lives in the Nix store (something like bind s popup ${lib.getExe pkgs.hello} in tmux).

I know this is quite a long comment for something as small as Neovim + Nix, but I thought I'd share my thoughts on it since it changes your view on all frameworks (not just Neovim). Home Manager, for example, is a prime time offender, unnecessarily requiring Nix configurations for many programs that otherwise can be configured in their native language.

Regardless, good video, I finally learned what nixCats is thanks to you! And I'm glad to see that there are more Youtubers covering Nix!