http://docs.pixologic.com/reference-guide/tool/polymesh/normal-map/
Sorry, please bear with the barrage of questions below:
Tangent: Since Zbrush is for sculpting objects, wouldn’t this always be on since you want to use the local coordinates?
Adaptive: High quality Normals. Unless for quick tests, when would you want this off?
SmoothUV: I’m not too sure what this is-- but I’m guessing you only use it if you turned on “SmoothUV” when subdividing? When would you want to (not) use smoothUV’s?
SwitchRG: (guessing it’s related to various piplines?)
SNormals: What does “Smooth Lowres Normals” mean?