Since ever I have been told to make assets as low poly as possible to save necesarry performance in larger scenes. Until now, I have never worked with LODs, because I used Blender for my scenes and therefore keeping things as simple was vital, but how important is that inside of UE4? And how many polygons should, for example, a LOD0 tree have?
Im asking this because I am not sure if it is worth it to model a far more detailed mesh specifically for the usage of LOD.
There is no definitive answer on this with exception that you want to setup LODs to squeeze out better performance where you can.
Some things to consider when making your LODs:
Know the quality bar you’re setting for your project.
Know what your target platform is and the target FPS you want to hit
Use up to 4 LODs (Base, and 2 lower LODs and a Billboard for the last LOD with foliage like trees)
Use the LOD screensize to switch at specific LODs when needed.
As for Polycount this is a subjective question that can only really be answered with some best practices rather than specific numbers. For instance, if you’re going to target PC then you can more than likely hit the higher fidelity mark without as much worry, where as someone with a lower-end machine may have more issues. I think 8180 is within reason, and depending on your quality needed may be a little lower than you would want.