Hey @IceDealer ,
I think you need to test out different combinations to see what works best for your setup. However, a few suggestions (what I would do):
- Create your buildings from the modular asset packs - make as many combinations as you want.
- Use the Merge Actors tool to create a single mesh out for the modular building
- Use this single mesh inside a HISM actor (basically you will have the same building repeat multiple times in your scene so they can be instances in the HISM actor)
- Build your city out of several HISM actors which contain multiple copies of the same building scattered around
Another option, do step 1-2 above but instead of doing HISM, use the Proxy LOD tool (new in 4.19) to combine far away meshes and reduce draw calls.
Then test between the 2 setups and see how it performs.
Another thing to look at is Level Streaming. You can have chunks of your city streamed in as the Player moves around. You can also do the inside of the buildings as a separate level and use level streaming to load interiors.
Occlusion culling happens regardless of whether you use meshes or HISM (as far as I know). Also, make sure you use HISM (not ISMs) as you can specify a culling distance in the properties (default is 0 so they never cull).
Hope this helps!