If I am doing an interior scene with no windows, therefore no sun, is it still advisable to use the VrayCAM? or should I just stick with the max cams and not worry about cranking up the multipliers?
I personally can’t do without the physcam anymore.
What i do is use it on a “normal” scene, even without sun and sky, and then expose it.
Either by hand, or most often with my exposimeter (OT sticky thread).
One multiplier to rule them all 
Lele