3D Box Size and Scale performance

I am building a 3D World Building game where you can build with different size blocks. I would like to have the blocks available down to 1mm so I am using a world size of 1000 for the xy scale in the 3D Behaviours for the objects. Some things will be built with large 1m blocks, while others can be build with blocks ranging in size down to 1mm.

Will I encounter issues with performance if there are too many 1mm constructions on the screen? Is there a way to predict what the limits are to avoid displaying too high a “resolution” for the blocks?

I just want to avoid trying to build something that is not possible.