A:
Yes, the Harmony Smart Control can control devices behind closed doors. You can use the app on your tablet/phone, or the mechanical remote that is included with the Smart Controller. Either the control hub or the included IR blaster must be placed inside the cabinet. Your remote or tablet/phone app communicate with the hub via wi-fi but still use IR to complete the signal path to your devices.
If you have devices inside and outside of the cabinet, then either the hub or IR blaster must be located inside and the other outside so both areas are covered by the IR signal.