Creating Cities with Interiors, Static Mesh vs. HISMs?

Hey,

Now I’ve done a lot of research the last couple days and haven’t really found an answer to my question.
Say I had a team of artists and I wanted to create a city. Some buildings can be entered and have interiors (much like in The Division)

There are several modular building packs on the marketplace and most of them are just Static Meshes placed in the level stacked together. There is the benefit of occlusion culling but once I place my Player Start on the roof and look over the city, the performance drops drastically.

What would be the best way of creating all those buildings ?

A) Static Meshes in the scene, easy copy paste, Occlusion Culling, Merge Actors, LODs and HLODs (clusters) (like here: Modular Houses - Open world optimization - YouTube )
B) Hierarchical Instanced Static Mesh Component for each modular piece inside of a Blueprint, hard to edit inside of the Blueprint but high performance and supports LODs.
C) Create Modular Pieces in Maya, create buildings out of these pieces in Maya and then export as one single mesh. Then use that single mesh as HISM instance in UE4 ?
D) Another way I haven’t heard of…

The problem really is once I am on top of a Building seeing everything. I guess if that wasn’t possible in the game the answer would be A. But to me B seems to be way more efficient performance wise but definitely not very easy when I want to edit stuff and add new buildings. Also since the HISMs would be rendered all the time because there is no occlusion culling going on (afaik) I would have a constant frame drop.

Maybe if I arrange the buildings smartly I could place the ones that have an accessible roof just between very tall buildings so I don’t see that much of the skyline to avoid a lot of polygons drawn at once. What do you think ?

Know I know this is heavily dependent on the city layout too. I was just thinking that HISMs would really reduce the draw calls to a point where its absolutely reasonable to use them with the modular pieces.

The interiors could be just static mesh pieces since they are mostly occluded by the exteriors anyways.

Can someone maybe help me with this ? I’m really really lost here. Thanks a lot for reading!