JaroslavMares The first thing you need to understand is that RN preview is completely detached from the rendering of the objects. Choosing appearance Original is almost never a good move as it will cause a very long preview cache calculation - the dialog informing about it is not a joke (See Rhino bottom info bar you will see RN is telling you "Display is updating longer than expected. Consider changing entity appearance." and that's why you think it doesn't work). It works best when you want to create initial piles/clumps/groups of objects to bake/remodel/optimize and then put those into another much bigger ecosystem. The best option is almost always Point Cloud as it is very light and at the same gives you a very good understanding of what you'll get in the render.
To do what you aim for you need to bake your ecosystem - Cycles currently does not support direct rendering with RN yet. At this point, direct rendering without baking is possible with Octane or V-Ray (some other integrations are in WIP).
A short guide explaining this is here: https://help.rhinonature.com/faq#how-i-can-render-created-scene
Although it was also discussed here: https://discuss.rhinonature.com/d/22-do-i-need-to-bake-using-v-ray-next/5
Plus on Rhino Discourse here: https://discourse.mcneel.com/t/rhino-nature-released/128543/57
Ah... One more thing after baking make sure to switch off ecosystem preview (the eye icon) as RN preview will look like an overlay when rendering in the Rhino viewport.
Hope that helps!
