I will have to try out instancedBufferGeometry.
Could one write a custom shader that makes Instances meshes appear completely different? From what I understand one can modify the vertices with a custom shader too.
That way one could only have instanced meshes in the scene. But change the shape with a custom shader.
Or is it only possible to have the same shader code for all instances? I found this InstancedUniformsMesh where it is at least possible to change the uniforms per instance.