Hey guys,
The splines are easily instanced in the level and all of the features are scalable! So you can turn tessellation on or off, moss painting, vertex painting, worldspace color/normals, tessellation fade, river depth and features, it’s all in there per material instance. Everything has LOD’s for it as well with cheap versions of material instances applied to the meshes. You can decrease the density of the grass or branches to suit your needs. Another awesome features, is after you build a tree, you can simply select all of the splines and export it as an fbx file. Then bring it back into the engine and re-apply the shaders to it and you can generate any or all of your trees that way. So you can apply custom animations to them, whatever you like 
I’m currently getting 30fps with the scene that you see above with all of the features enables on all of the material instances and real-time sun shadows. I’m using a GTX 760 Graphics card. Hope that helps to answer some questions!