Thank you for answering. Guess I am not messing with that then, more complex than I thought it would be.
Btw, just watched your talk on YouTube (NixCon2023)

• How is the state for checking for partition alignment automatically? For example does it warn me when partition is not aligned?
• I heard it is possible to use YubiKey with luks2 in disko, is there any documentation example for that?

Also, I have:

nixosConfigurations = {
      book-of-the-azure-sky = lib.nixosSystem {
        system = "x86_64-linux";
        specialArgs.inputs = inputs;
        modules = [
          disko.nixosModules.disko
          <...disko-config.nix here...>
        ];

and disko-config.nix:

{
  device ? throw "Set this to your disk device, e.g. /dev/sda",
  ...
}: {
  disko.devices = {
    disk.main = {
      inherit device;
      type = "disk";
<...>

How to use disko-config.nix in modules and set the device in disko-config.nix to /dev/sdb?