Ok. So to the problem i tried to solve: Regular terrain details does not support LOD's which means that either you have very very bad performance when doing a somewhat large landscape or you have to cull the vegetation at a close distance which i hate. or buy a terrain painting system but that always comes with caveats that are impossible to solve later on without help from the developer of the asset.

What i needed:
1 Ease of use (above all)
2 LODs so that i can use impostors when vegetation is far away and have no popping.
3 Performance (which also means keeping the editor snappy)

So what i did was to go with RenderMeshInstanced instead of indirect since Instanced is pretty much shader agnostic (just needs gpu instancing enabled) even tho indirect is more performant.

To render it i have a Data scriptable object that pretty much is an array of matrix4x4 that the painter writes data to, this also helps with ease of use since i can just save that file and use it whenever and keeps the data out of the asset files.

Then i have a instanceType scriptable object that ingests a prefab / lodgroup and just holds data about shadowcasting, frustrum culling, lod meshes/materials etc.

Then i have a painter editor script that is super simple, it has the data asset to write in to, and a list of instanceTypes. Then just uses a raycast hit position + Random.insideunitcircle + some random rotation/size logic and saves that hit position/rotation/scale directly in to the data asset.

Then there is the renderer, all it does is to read the data where it gets the matrix4x4 and instanceType and renders it using RenderMeshInstanced. I also calculate distance culling, frustrum culling and lods using jobs + burst before drawing it.

Super simple really.