@matan19 With World Composition it will bake the landscape material final appearance into one texture per tile, so you will need to compose several textures tiled together to form the whole landscape and use graph math to know which one to sample at that coordinate set for that tile. That project I mentioned I guess was using that, because there are differences into landscape it shows, something that you can realize better in play mode.
I wish there would have a better way to have that easily done, since it is an essential feature for any game project, not just open world. Maybe @RyanB could add some insight into this, I am not sure he was in charge of this particular feature at Fortnite, but he is experienced enough with such material types.