I have used “Sky light” and “Directional Light” for GI.
With regard to settings:
Static Lighting Level Scale : 0.8
Num Indirect Lighting Bounces : 100
Indirect Lighting Quality : 5
Indirect Lighting Smoothness : 0.6
All default values in BaseLightMass.ini
Light Map resolution for complex/large objects (Sofa, Floor, etc) - 1024
Rest are default