Unreal Engine - CUBE GRID - Never use BSPs again!
Unreal Engine Level Design - NEVER USE BSPs Again - In fact, don't watch any of my old videos on them, they are useless garbage which will ruin the performance of your level.
Use Cube Grid Instead and Bake Static Meshes so you can make use of instancing and all the great new features Unreal Engine 5 has to offer. :)