I believe the CAM Styles can define the defaults for the Machining folder that MOP's inherit when added. When I view the System tab in any new or existing .cb file, expand the CAM Styles folder then select from the Standard-in folder the unnamed style at the top, which is the default style and compare it to the PCB isolate style, you can see how it differs from the default style. Same is true if you are looking at the Standard-mm.
The PCB isolation style sets default Machining MOP parameters tailored to and typically "in the ballpark for" isolation routing. You can make changes to any of these listed styles (or create new ones) to suit your "general starting point" purpose.
Associating the .cb file's Machining folder to a Style Library and Style helps to save setup time and configuration for a MOP.
I've never used them but after your posting the question and looking into it, I may just start.