Please start by reading All on One
The audio server computer does not need Steam installed. You can run the audio server on it since it has no dependency on Steam whatsoever (some people call this DRM but that's another story).
For the audio server you need to copy the following files:
Now if you want the easiest possible setup, you can add the audio server manager to start when windows starts. Right now it's a CLI program, in the future it might get a better GUI but really the GUI you are to use is the controller so this is not really important.
The player computer needs Steam to be running to validate DLC ownership.
The player manager on the other hand does not. You can add the player manager to Windows start-up in the same way as the audio server manager, see above.
The controller does not need Steam installed on the computer. So you can take the controller EXE and data files it needs and copy to another PC.
You need to copy the following files:
The data archives need to be in the subdirectory pro_controller relative to the EXE file.
Launch the controller from within Steam itself can cause problems in a multi-system setup. Steam will detect that player is already running on the other computer and then disable player's access to DLC. Steam thinks running on the machine with the Controller is the currently running valid version of the application. To mitigate this, launch the binary directly outside of Steam. Using a shortcut to Controller created by the launcher has the same effect.