Clean install

[Robusti]

Is it better to install CoD and all the campaigns then the mod or fresh install then mod then campaigns?

[ATAG_Colander]

The vanilla game uses:
"My Documents\1C SoftClub\il-2 sturmovik cliffs of dover"

The mod uses:
"My Documents\1C SoftClub\il-2 sturmovik cliffs of dover - MOD"

You might want to install and run the mod once (so the folders are created) and then install the campaigns to the mod folder.