I usually use .001 mm absolute tolerance. That might be unnecessarily tight for display purposes though. Any recommendations?
If the goal is only visualization, then it is somewhat subjective which tolerance produces visually satisfying results from your definition. If everything is meshed in Grasshopper, then you can already check the final geometry in Rhino (Bake and Rendered mode), the meshes will be identical on ShapeDiver.
In general, the tolerance will only be significant if you are doing sensitive operations on the meshes (cuts, intersections, etc…). It is probably fine if you keep working with your usual settings.