Robbie why dont you tell us the model of light you are using it might give you a better under standing. Exit sign come is standard voltages 120v,277v even dual tap (120v/277v) so the circuit will still require one hot and a neutral and a (non-switch) for the EXIT Sign. You mentioned that the light will be Plug I dont think that a plug light is concider for life safety. Think about it if it plug it can be easily unplug and serve no purpose. now when you said plug you meant hardwire?
Regards.
