Premium Choice is less about full formats (except for what they provide for HD2 channels) and more about workparts. Stations pull in playlists that are configured for them by whoever is in charge of a particular station's programming, and the data is loaded into Selector for that station with its breaks, service elements and such. They can also select local talent or voice tracked talent in the right amount for the individual station.
That's why the major iHeart stations that use elements from Premium Choice generally have individualized music lists (often driven by local research) and different talent lineups and even different stopset placements.