With Guix you have reproducibility, freedom, good docs and peace of mind, also when configuring things more deeply. You also have a powerful programming language (Scheme / Lisp) with which to define your system config as well as your dotfiles. This is my insight after years of GNU/Linux usage. I run Guix on laptops, desktops and servers, and I never have configuration drift, as well as the benefit that I have a self documenting system.
By default it is, but there are many non-free channels you can use to add the OG Linux kernel to your Guix install as well as nonfree drivers. A famous one is nonguix, which i also use in my config. They also make custom ISOs with the Linux kernel, which helps some hardware indeed. So the libre only policy is a non issue if you read into it a little, but unfortunately most people stay at surface level