Please explain me this: (Normal map, XN, UE4, settings)

mzprox

Here is a guide for normal map baking for Unreal 4:

https://docs.unrealengine.com/latest/INT/Engine/Content/Types/Textures/NormalMaps/Creation/index.html

I could follow it, but i'd like to understand it. Also I'm a Blender user, so if possible try to explain it in a way so i can get my models from Blender right.

Questions:
(fbx export)
1, One smoothing group? Does it mean that the whole model is smoothed and no hard edge? (Blender smooth shading, no edge split)

2, tangents and binomials option unchecked. What does that switch does? what would happen if i left that on?

in xnormal
3, says 'use exported normals'.. but in this case i gues they are same as averaged normals, right?

Unreal engine specific
4, what do these options do? import explicit normals checked, import tangents unchecked.

Thanks