Using Height and Normals from Substance Painter together

I was wondering what is the correct way of using the Displacement (height) map and the Normal Map exported from substance in a Arnold Standard surface shader.. together.

To be precise, I do know how to hook them up and all. 

It's more about how to make sure that the Normal map only creates the finest details. I'm not even sure you are supposed to use them together. Would a correctly  set Displacement with autobump already do the job of a normal map? Is using them both basically redundant?

Once you create actual height variation, are normal maps necessary? In zbrush I remember having the option to bake the normal Map only for the highest subdivision levels of detail. Is there a way to do something similar in SP?

Is using Displacement without autobump in combo with a normal maps better then using Displacement with Autobump and No normal map?