Also correct me if I'm wrong but I think Guix goes further on reproducibility than Nix, because everything they package is from source, whereas my understanding is that a lot of Nix packages are built from binaries.
TinyTeX is a custom LaTeX distribution based on TeX Live that is small in size (about 61Mb on macOS/Linux, and 94Mb on Windows when (g)zipped), but functions well in most cases, especially for R users. If you run into the problem of missing LaTeX packages, it should be super clear to you what you need to do (in fact, R users won’t need to do anything). You only install LaTeX packages you actually need.
Reproducibility is a big topic for Guix developers and users as well, just have a look at how many times they talk about that: https://hpc.guix.info/blog/2022/07/is-reproducibility-practical/
Also correct me if I'm wrong but I think Guix goes further on reproducibility than Nix, because everything they package is from source, whereas my understanding is that a lot of Nix packages are built from binaries.