I'm gonna be honest, I use NixOS, but the docs fucking suck, and a number of things are just broken in nixpkgs. For instance, I recently discovered the structuredExtraConfig option for patching the kernel straight up does not work. This means you cannot unset any kernel options, which means some kernel patches won't work unless you manually supply the entire kernel config.

EDIT: what's even more annoying about it not working is that it fails to apply silently. In other words, your kernel tries to compile and then an hour later it fails because your config changes weren't applied.