What is the operational order of the Contact Delete process for Marketing Cloud?

A developer identified duplicate contacts and initiated a Contact Delete process for 10 million subscribers. How could the process be expedited?

A developer created a landing page in CloudPages which return unique content when subscriber data is located on a related data extension. The developer does not know if all subscribers have rows in the related data extension, and want default content to render if no subscriber data is found on the related data extension.
Which best practice should the developer follow to control the unique and default content?

Northern Trail Outfitters uses a Send Log and sends more than one million emails per day. They want to execute daily reports on all subscriber activity without impacting send performance.
Which set of best practices should be implemented''

Certification Aid wants to encrypt data stored in Marketing Cloud. It is fine if unencrypted fields are visible to Marketing Cloud and Salesforce users, but the underlying data should be encrypted at rest to prevent physical data theft. Which encryption method should be chosen? Choose 1.