RTF is a global modification that replaces all towns in the game.

Regarding storm elementals, I think they are fine as they are, just give them more projectiles.
As for the fog elementals, I would give them incorporeality; it suits them!

It also suits all air elementals, and you can't just give it to them because it suits them; it's better to reduce the stats of the ice elementals.

Added after 7 minutes
I compared the stats, and the fog elementals win in terms of speed and initiative. I made the stat range larger.