Hi David,
Any interaction, whether it is simulation or even light, anything related to size, typically follows real-world size for many years now. Back in the days, it was just units. There are cases where large or small might challenge that idea. Here, the project scale can be useful.
To determine that before is a good idea, as changing the scale later on might not affect all settings.
Besides, if you have a super large model, perhaps explore the idea of Redshift's camera option.
The Camera Space Render.
https://help.maxon.net/c4d/2026/en-us/Default.htm#html/VPRSRENDERER-REDSHIFT_RENDERER_TAB_GLOBALS.html#REDSHIFT_RENDERER_RENDER_IN_CAMERA_SPACE
While the precision in the old days was a little bit lower, the rule was three digits before and after the period (or comma - depending on your localization) was the guidance to go with. Today, it is more of an idea to see if the scale of the Project might be in need of a change.
Project scale:
https://help.maxon.net/c4d/2026/en-us/Default.htm#html/DDOC-DOCUMENT_GROUP_PROJECTSETTINGS.html
My best wishes for your work.