RGB is the combination of primary colors which make up thousands of colors and tints.  For the color chips in the material room, those numbers arrange from 0 to 255.  For your lights, that range is 0 to 1, 0 for all RGB being no light color (black), 1 for all RGB being each primary at the same level of pixel intensity creating white light.  So, if you want white light, set each primary color to 1.  R = 0, G = 0, B = 0 produces black; R=1, G = 1, B = 1 produces white.

When you active Ambient Occlusion, use the default setting already selected on the pallet.  That should cover most normal scenarios. 

For the IBL, yes, shadows should be unchecked.  That will gray out the raytrace and depth shadows.  By default, when you select IBL for your light, the shadow box will uncheck automatically.