A mbient light permeates a scene and illuminates from all angles equally without providing contrast.

Photometric lights are designed to simulate light sources exactly as they behave in real life by loading and using an IES (Illumination Engineering Society) file with details about the light's behavior, such as how the light passes through lenses and its intensity and falloff.

Check the VRaySun page for more information. For the fog I would use a BoxGizmo with a VRayEnvironmentFog, there should be tutorials out there with this info. I've pulled effects like that off before with a VRay sun light, but I think you can do it with a disc also.

A Sun light is a spherical light source placed at a specific location which simulates the sun in the sky. Yes you should never use the max lights with VRay, I think it'll always get you in trouble.

A dome light, which creates light within a dome shape to create a traditional global illumination setup, is also considered an Area light.

An Area light can have any one of many different shapes: plane, disc, sphere, or the shape of a mesh object. Area lights are useful for simulating man-made light sources in an interior environment, such as lamps.

Vray light mtl 3ds max