I don't agree with occupant vs building.  There are special cases where the building may be historic and actually has a name -- but the shop is different than the historic name of the building -- and this would make it very difficult to map both without my method of building not merged with shop.

Just a comment about "both" -- meaning both a node and an area -- the intent was having the area marked as a shop and have the poi marked as a shop -- this is double tagging and is very frowned upon.  However if the building is a building and the shop is a node, this is no longer "both" and it also opens the possibility for multiple shops in the building.

Yes the apartment complex + shops at level 1 is actually very common and becoming more common in high pop areas.  I tag the building as apartments and put however many POI shops on the building.  This should be fine too.