Well, that’s not a great example, because all of those were once corals that have since bleached and died. Underneath all that would be the scape which they grew on.take a pic of a coral reef w/o corals, this is what your hardscape should look like, overgrow it in corals & viola, a reef
Naturally, reef-building corals go through a cycle by which they erode over time via boring organisms and bacteria weakening the base. When they collapse, they slowly continue to erode until they become a part of the bottom sediments, where new coral larvae settle. Although corals do ultimately serve as the base for coral growth, the picture here does not completely describe a natural reef scape.
As far as going with NSA, HNSA, or neither, do of course what makes both you and your fish happy. You’ll definitely want to think long-term, especially if you plan to populate the tank with corals, but the scape can change overtime. That’s what happened with my Fluval 13.5. I initially wanted to have a big arch, but eventually I realized the inconvenience and limited territories that this scape provided. Instead, I chose to make the scape more natural, in which the rocks piled on top of one another in a cascading look.
When I upgraded to my 40B, I wanted one side to be tall and complex, while the other is more open. This offers a healthy mix for various types of fish.