Use the scattering inside coronaMtl, it behaves the same as volumemtl and you dont need to use blend.G is the same as vray phase parameter in the help you linked. Generally there is no reason to change it from defaults except when you are rendering clouds, then you should increase the value to get the silver lining effect - see attachment
Use translucency for SSS media (skin), regular refraction for scattering liquids (juice), and CoronaVolumeMtl or CoronaMtl with black opacity for media without defined border (fog, smoke, clouds)
this happens sometimes, the UI is not totally intuitive right now. We are trying to find out if it could be improved. You can try setting absorbtion color to grayalso sss mode checkbox currently has no effect