Not really. I’ve not tweaked anything related to performance - because I’m not even sure how I would go about doing that on Guix. This makes it really easy for me to switch to custom kernels, so that’s just it. Right now, I have the option between default non-free and XanMod. Someone could package Zen or TKG on Nonguix, and that would increase the kernel choices. There’s also this option to switch to an entirely different kernel architecture, like for example, Hurd, but that probably won’t work on metal.

Compiling kernels makes no sense anymore.

Back in the days - Linux versions 2 and below - the kernel was much less modular, and resources wasn’t as plentiful. So it often made sense to build kernels with the stuff you needed statically compiled for speed, and the rest left out fo save memory and shorten boot time. Not to mention, Lilo (the thing we used before Grub) had limitations with respect to kernel size.

Nowadays, Grub can load a kernel of any size from anywhere on the disk. There’s plenty enough memory and CPU to leave the kernel core slightly bloated with stuff almost nobody needs with zero practical impact on boot time and memory usage, and most everything else is compiled as modules and loaded as needed - again with next to no boot time or running speed impact.

If you custom-build a kernel today, you’ll boot a tiny bit faster and it’ll run a tiny bit faster, and you’ll have a tiny bit more free memory - all of which you will never notice. What you will notice however is that kernel updates are a PITA on a regular basis.