> From my understanding, emacs-guix just eases the install of the
> non-elisp packages, e.g., guile.

No, emacs-guix is simply an interface to Guix, it allows you to install any
Guix package, Emacs-related or not.

> If I install the non-elisp requirements with Guix then emacs-guix from
> MELPA, it should work the same, isn't it?

No, because the MELPA version and the Guix version are not the same and the
requirements might be different.

Emacs package management is rather simple while Guix gives you much more power,
including reproducibility.  If you install everything from Guix, it gives you a
fairly strong guarantee that things will work out of the box.

-- 
Pierre Neidhardt
https://ambrevar.xyz/