Hello and Happy holidays to everyone...
I was quite busy so I did not have time to read this thread, and sorry for not replaying sooner...
Considering edges, and grass going over it - maybe it could be solved if we have Corona distance shader for C4D and I hope developers will include it as soon as possible (I also need that shader for another plugin I'm working on :) ). For now, way to do it would be to create another surface for grass that would be smaller for radius of grass patch. In that way all the grass that goes over the edge of new object would be actually next to the edge of old surface. I hope i explain it good :)...
Considering realism - in GK III you can always tweak materials... You can add textures or colors or variations (in variation shader) to your liking.