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

Okay, agreed. Basically, all the enemies you encounter are recorded in a bestiary, and you can always view them, play their animations, etc. Also, the lore is interestingly revealed in the books you find during the game. By the way, the game is mostly populated with units from Dark Messiah, Heroes 5, and Heroes 6, and as I understand it, the developers didn't bother creating new models but simply transferred them to Might & Magic X.
As for what's new, they interestingly showcased the Elves: the female elves, as I understand, have completely new models, while the male elves are a recolored and slightly edited model of Raileigh from Heroes 6.