When plugin is activated, on setting page containing Assign Capabilities there is no default setting for administrators (and other roles also), and it is understood that administrator should have all the capabilities.
I suggest that there should be preset default setting for each user role, what the developer think they should be. site admin can always these setting on plugin activation. If it is desired that site admin should review default setting, a message can be displayed in setting page or dashboard.
I further suggest that there should be an option to revert to default setting, should a site admin get lost while tweaking capabilities.