Planetset - Terrain | Sky | Water | Instancing
Does it rely on Cycles displacement?
No, you can view the terrain in the viewport just like other regular objects:
I get a kernel timeout error when using GPU rendering...
This can happen on some systems when rendering large volumes like clouds. There is a fix for this described here, however it should be taken at your own risk.
Does it work with Eevee?
No. PlanetSet is designed to work with Cycles. It is not recommended to use Eevee for scenes containing large amounts of geometry or complex materials.