Same 5,000 cubes, two ways. Separate meshes = one draw call each → the CPU drowns. InstancedMesh = one draw call total → the GPU coasts. Raise the count and switch modes — watch draw calls and FPS diverge.
Both modes draw identical geometry. The only difference is how many drawElements calls the CPU issues per frame. Push the count high in separate mode and the FPS readout tells the whole story.