How to tag an area with residential levels on top of shops?

I see TZorn's very reasonable answer has already been upvoted and accepted but I'd like to offer a different take.

My experience comes mainly from New York City which obviously has very high density of both residence and commerce. There are purely residential neighborhoods and purely retail/commercial/industrial areas, but a lot of the city, especially closer to the centre, is mixed zoning. Early NYC mappers found that trying to classify all of the city's landuse was counterproductive and prone to disagreement, and arrived at the following "standards":

• For residential/retail/commercial landuses, only draw and tag if they are formally named and have distinct boundaries.
• For other unambiguous landuses, most prominently industrial and religious, tag at-will. (But note that this requires ongoing maintenance as the city's industrial areas are slowly being repurposed.)
• Omit landuse tagging in other situations. Let the tagging on the buildings and POIs speak for themselves.

Just to be clear, I don't think this is the only valid solution. But nor is there a law that says every square inch of the Earth's land has to be tagged with a landuse, and therefore we have to just assign the best fit even when it's not 100% true. Leaving off the landuse tags altogether is similar to using building=yes -- sometimes there isn't a more detailed tag that's accurate. (And in fact I wouldn't have a problem with landuse=yes to distinguish between used land and unused land.)

Speaking of buildings, you also asked about building types. I'd be perfectly comfortable using building=house for the top picture (or building=terrace if you want do them all as one element) and building=apartments for the lower picture, and then adding the businesses as nodes. The map will speak for itself. But obviously falling back on building=yes is also fine!

This type of question has been asked frequently in the past. See for example answers to : Tagging landuse in downtown areas.

Your nice pictures I would unequivocally tag as landuse=retail (see my old answer above).