how about turning off texture streaming? I did it in a level with a humongous landscape and a small landscape, not lots of meshes / material, and it’s working fast. You know, texture streaming is basically a method that the engine uses to render textures based on what’s in the current screen view. It’s actually intended to reduce rendering slowdown, I think, if there’s lots of multi-textured assets in camera frequently. Using 4K shouldn’t slow it a ton unless there’s another issue, or if the streaming pool size is too low.
Those models and materials look rather scant as far as memory usage, so try checking the streaming pool maximum size and increasing it…or simply turn it off. If neither of those work, use visualizations of the materials and lighting…plus the stats tables of rendering and memory allocation to see if there’s something or a few things using up a huge amount.