What is exponential height fog?
Exponential Height Fog creates more density in low places of a map and less density in high places. The transition is smooth, so you never get a hard cutoff as you increase altitude.
Where is atmospheric fog in ue5?
Atmospheric fog has been deprecated in Unreal Engine 5, you should use Sky Atmosphere instead. Documentation for Sky Atmosphere can be found here. In addition to Sky Atmosphere, you may want to look into volumetric fog which can be found here. I hope this information helps!