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

Will only the Dark Gnomes be changed, or will all the currently available factions be affected?

Not all of them; the Elementals will remain unchanged (except for the removal of the gate-opening mechanic), and I want to merge the Lizardmen with the Nagas, using the concept of the Ashan Naga-Chaos faction as a basis, who want to flood Ashan.