Materials Compile vs Runtime Cost

Can anyone explain to me, in general, what things inside the material editor cost only compile time and what things are actually going to cost me run-time performance (frame rate)


I am making a material for landscapes but this game is for the oculus rift so run time performance is extremely important.

I really like the functionality of layered materials, but I read that they are very expensive at run time because all textures are rendered before being blended. (this is explained at the bottom of the link below)

Is a material only considered “Layered” if you use the actual MatLayerBlend functions within the editor ? does copying the nodes from two materials into a single material and lerping between them have the same performance issues?

And finally, do landscape layers share the same performance problems ?