Views OOP approach - Let Views extend from Meta/Parent View
When you change something on any of the different displays (other than master), there should be combobox at the top that says "for" which defaults to "All Displays" meaning that the change will apply to all displays. But you can select "This Block" or "This Page" so that the change only happens to that particular display.  

Also, if you go into views settings "admin/structure/views/settings" you can set "Always show the master display" which I usually do.