Does placing hundreds of small landscapes like static meshes cause performance problems?

My game consists of hundreds of skyscraper rooftops or semi-outdoor floors.
Placing different small landscapes (with the same material) on each rooftop
is probably the most appropriate usage for me for convenience.
Does having hundreds of small 7x7 landscapes like static meshes scattered around the world cause any serious performance problems?
Anyone have any experience with this?

I would say it will and I think that the use of mesh instances would be best case here. You can do this by selecting a rooftop mesh, selecting actor in menu and using merge actors. Expand window to the right for options. Then when you place that actor, click the mesh component in the details tab for it and duplicate it. This creates an instance of that mesh inside that actor which computes way faster.

Sorry, maybe I didn’t express clearly enough, I meant to place hundreds of small landscapes, not meshes.
And I also tried, to merge landscape with mesh can’t make the material work right.