Optimising Panel Based Buildings

Hi recently I built a very large structure made of panels in Blender. My game is quite far in and we have noticed this structure really hogs the FPS when in so I wondered on how I can improve this. We went for panels due to the ease of assigning/creating textures for square layouts.

I have enabled Occluding with bake and do get some FPS back when facing away from the structure but I think my Occluder size is too small for the panels. Occlusion Bake took a very long time to complete so I'm thinking I want to avoid doing this often which will happen a lot as we add to the game.

Does anyone have advice for large structures, something I have read about is shared meshes. Will I get performance boasts by using a single mesh instance for my panels of that type?

Currently we copy and paste the mesh panels in blender and unity imports each mesh as its own game object with unique mesh assigned. If I assign a single instance of the correct mesh to the mesh render component on each panel of that type will I gain any advantage?

Do multiple shaders assigned to a single mesh slow things down, maybe we should try to use a single shader per mesh with images made with the parts combined?

Also does tiling of the images in a shader effect performance?

Maybe panels is bad idea and we should try to make long stretches of walls with meshes combined?

Thanks I will be testing this stuff myself, just wanted some input from those who might know on how to build easily and effectively whilst having best performance. ;)