As nix is also a source based package manager, you can also just disable the binary caches and have everything compile on machine! I don’t think you would get of the benefits of compiling it for your hardware though due to the sandboxing of the build environment.
Everything has to be compiled on Gentoo, right? So would the many binary nix packages even work?
Sure, binary packages always worked on Genoo. Binary packages are the result of compiling.
By now you can freely mix and match precompiled binary packages and selfcompiled packages on Gentoo.
As nix is also a source based package manager, you can also just disable the binary caches and have everything compile on machine! I don’t think you would get of the benefits of compiling it for your hardware though due to the sandboxing of the build environment.