The apps is used to electronically control engine speed - no actual mechanical connection to control fuel flow as in earlier years - all done electronically - the APPS is in reality a large "volume control" like on a stereo - turn it up "louder", and the engine speed increases...
And yes, use of cruise control SHOULD minimize wear on the APPS/TPS, except on older systems that still merely apply mechanical/electronic control of the TPS/APPS, rather than using other circuits inside the ECM to do it separately...