The CGR and Approximate format contains only the graphical representation of the geometry. These options allows you to choose different appearances of the linework of your Drawing.

The CGR files are facetted models for visualisation that can't be edited but they can be used for interference checks. It can also be used as a light representation of a native model that is too heavy for the computer to load, so it is helpful with big assemblies. 

The Approximate mode reduces memory consumption and it consumes even less memory and is faster than CGR.

To edit this properties go to the Drawing and right-click on the frame, then select "Properties". Scroll down in the new window and look for the section "Generation Mode". Below you can find the "View generation mode" and from there you can choose CGR or Approximate view.

 How to create a dimension relying on a 3D point, projected in a view in approximate mode?