New at Rhino here : How to handle "thousand million" poly models and distibute trees?

Handling files with huge number of heavy objects and scattering/distributing these objects are two separate (but related) problems. Rhino is definitely capable of the 1st one, the 2nd one currently can be only done with some custom scripting or Grasshopper. There is RhinoNature plugin “in the works” but it will probably be a while before it is released/production ready.

For rendering, you definitely need to look at blocks that contain simplified geometry, and for rendering, use of Proxy objects of heavy meshes that load only in render time… Rhino does not have proxies by default, they are offered specifically by render engines, like Vray.

@JimCarruthers - in the gallery examples, all of the models including massive amounts of entourage elements, are created and distributed in Rhino, but with use of some custom in-house scripted tools, so while possible, it is not easy workflow with vanilla Rhino.

I wrote a long-ish post regarding methods to handle heavy files in Rhino a while ago, perhaps it could be of some help for you: