There are 9 different fog zones. Global, and 8 others. Global will be selected when opening an OldDark mission with fog, but I don't think there's any technical distinction between that and the other zones. Values are set in Editors > Mission Variables > Fog Zones. Fog zones are assigned to rooms in the Weather > Local Weather property.
Precipitation is still limited to 1 type so it works the same as in OldDark.