Hello
I believe you have your response right below 
Blender, like the other similar DCCs such as Maya, Max or Houdini, is a non-real-time rendering software, the rendering is done on a separate step of the workflow. it’s by no means a real-time engine
While Scatter5 is currenrly the best scattering plugin available for creating environment in blender, I believe that blender is not suited for your expectations.
Having distance-driven LOD in b3d for your instanced trees is one of these expectations, as LOD’s are a typical game engine technology where the goal is to ensure a constant framerate for the player/viewer.
You can read more in this article
I’d go even further All attempts to implement LODs in blender via plugins or geometry nodes are gimmicks that will never match their game engine counterpart, you can trust me on that you’ll waste more memory and computing power than is actually necessary in order to accomplish the ray-tracing calculation.