As far as Fog Table Emulation, again it depends on how potent your computer is. Here is a good definition of what Fog Table does:
Fog table emulation (Volumetric fog): This setting allows the video card to render fog, smoke and mists in individual polygons, instead of flat textures.
· Image Quality: Fog table emulation will definitely improve your image quality, by making fog, smoke and mists appear in 3D.
· Performance: Fog table emulation can decrease your performance substantially, depending on the amount of fog, smoke and mists being rendered in the same scene at the same time.