You can access the hardware
special argument in the Nix modules of your
machines. This argument contains Nix modules that can be imported into your
machine configuration. Each module defines a set of opinionated defaults, such as
the file system layout, the bootloader, the kernel, the init system, etc.
When possible, the hardware modules also define a disko partitioning scheme, which can be used when installing the system using the install command which is a wrapper around nixos-anywhere.
The available hardware modules differ depending on the host system, whether the machine is a NixOS machine.
You can find the list of the available modules in the hardware modules reference.