In the GA documentation PR, there was a comment:

I'd insert a table here explaining the top-level fields (which are then explained below): istio, threescale. And then another table showing the first level fields under istio - such as global, gateways, mixer, pilot, ...

Lets use this task to fill that idea out and figure out how to update the product and community documentation appropriately in order to make the install option information more easily discoverable.