First of all thank you for your post
Some time ago I followed that tutorial completely.
But in those videos they use the BSP blocks to build all buildings (walls, doors etc).
Other people told me that it is incorrect to build with BSP blocks, it could result in performance issues.
Therefor, my question is: what is the correct way.
Build in Unreal with BSP blocks or build some rough architecture and import them in some 3D-moddeling software to create “models” from those BSP’s.