curious about InstancedStaticMesh

I don’t understand it theoretically and I’m not sure how the hierarchical instantaneous mesh and instant static mesh differ from each other in different situations…
As far as I know, they use multiple mashings like buildings as hierarchical instant static mash
I think the BP setting inside is the same… I attached the hierarchical instant static mash I made, and the image of the instant static mash.
And I’m going to use instant static mash and nanite
Is there any issue about this? It’s a problem…

and I following this tutorial Unreal Engine 5 Tutorial - Instanced Static Meshes - Tips & Tricks [4/4] - YouTube

I tried that way for make instanced static meshes but if I selected a lot of different meshes it doesn’t work with bacth of actor merge. but if I selected same meshes, it is work