What is the best way to design and build 3D levels with as little performance impact as possible

I am making a level for my 3D game using the Paragon game assets however these assets are quite heavy on my system performance. I only have 3GB VRAM so yes I understand why I get performance issues ,but is there some way that could make the performance a bit better. My level size is roughly the same size as the Monolith map from Paragon. Is it possible with 3GB vram or am I out of luck?

Lower texture resolution, reuse assets as much as possible, and keep the number of unique assets down. Setup and use LODs. Bake lighting.

Make a base character, and then child actors with different meshes. You could even have a single actor which sets the Skeletal Mesh depending on what you want. Then you only slightly have to edit child actors. Usually textures can be resized to 512 or 1024 resolution, there is a plugin on the market for this too (ImageResizer), you only have to set the normal maps to normal again after resize. Also in my opinion, in most cases you usually only need the diffuse and normal texture, you can setup roughness, metal, values with a constant material node if needed.