There is a lot of examples of different 3D configurators in Demo section of this forum, here is one of the latest ones - Architectural 3D app. Country house configurator
As for file formats, some of CAD tools support GLB export, one may also use .obj or even .stl (which has no textures though) to use with Babylon. Personally for me, when I worked with CAD models, most convenient pipeline was export to FBX and then import to C4D (or Blender if you prefer) for optimizations and texturing, then export to GLB.
Here is just one of numerous links how to optimize CAD models for rendering - 6 tips to optimize your CAD model for rendering - Meshmatic