Test differences between UStaticMeshComponent and UInstancedStaticMeshComponent
Open InstancedTest map and then play with the Divisions parameter on the BP_CubeVolumeSpawner actor (set to something between 1 and 30... though note anything over 16 takes a while for the construction script to complete). When monitor rendering stats when the Instanced parameter is enabled and disabled.
Run stat rhi in the console to see DrawPrimitive calls. When Instanced is used, far fewer calls are made to DrawPrimitive. If you are viewing in PIE (Play In Editor), make sure BP_CubeVolumeSpawner is not selected while looking at stats because the outline rendered creates extra rendering work.