Optimizing Unity Showroom or .fbx 3D Models

I'm trying to build a showroom for my .fbx 3D models with Unity.
My problem is that my files are way too big. I have almost no problem putting 18x 10MB 3D Files into my VR-Room but with 2x 50MB Files it gets shaky and laggy.
Furthermore I have models which are 250MB big. I already changed the Quality and Texture Compression (ASTC) in Unity.

The models are built with "Autodesk Inventor" and rendered with "Keyshot". 

My questions:

- Are there more settings in Unity which could help me optimizing my Application? (I'm no Unity expert so I dont know the settings in detail)
- Are there better options to build my 3D Models?
- Which size/polygon count would be optimal for many 3D models in one room?
- Would it be possible to stream the app from my PC to the oculus quest?
- Any other tips?

Thank you very much in advance!