Hello... Use the sound card/chip APP in Control panel to "re-task" the case front connector as a speaker/headphone connector... typically you can right click the connecter icon to change it to something/anything else...
Use SOUND-playback app in the control panel to enable or disable multi devices and outputs... in the OS.
You change your physical Input/Output functions, on your MB and Case using the sound card/chip APP.
You add/remove/disable/enable OS outputs using the OS Sound APP... or changing your Output connections/wires from the computer.