Hello Fozwroth,
So tessellation is currently not functioning in the preview release, and this has been reported (UE-25334) which is going to affect the quality of World Displacement since there is no way to increase the Vertex count for your landscape.
With that being said, follow the set up I have provided to get your World Displacement to function correctly. You will always want either a displacement map, heightmap, or pull from the red channel which holds those values of information.
Vertex Displacement
As you can see I have created an Scalar Parameter to increase/decrease the displacement intensity. Below is an example of this occurring when applied to a landscape actor.
Let me know if you have further questions.
Thank you,