I feel like I should note that changing the length setting makes no changes to blender other than how it displays information. A 2 meter cube is still 2 meters. Blender just shows that 2 meters as 2000mm. If you’re using imperial a 2 foot cube when set to inches will show as 24 inches. So it doesn’t change anything other than the units you are working with. Some physic system like rigid body and cloth have problems with really small and very large meshes do to precision limitations of the CPU. In these cases we change the Unit scale. I personally like to set length to adaptive, because I want to do 3D animation and will be dealing with multiple objects at different sizes and I’m in the USA so trying to remember that 0.1 is centimeters and 0.001 is millimeters is difficult. That’s also why I use advance mode with my transforms so I can just type Imperial sizes and let Blender convert it to metric. I don’t change it to Imperial, because so far everyone I’ve done any work with uses Metric system. Let me know if you want more info on Unit Scale.
