To build a list of communications preferences updates you can 

• Add a new activity list
• Filter the list for Activity type equals 'Communication Preference Confirmation'
• If you only want updates made by the constituent themselves add a filter for Entered by equals 'Self Service'

This is an example

To find people who have not updated their preferences - you can

• Tag everyone on the list you have just created above - see this
• Then create a list of constituents who do not have that tag