For monitoring customer status and making decisions within a journey in Salesforce Marketing Cloud, the entry source's data extension must have a primary key and a subscriber key. These keys ensure that the data is properly linked to the contact, allowing the journey to reference and update status data accurately as the contact flows through the journey.

To honor the opt-in communication method of subscribers in Journey Builder, Northern Trail Outfitters (NTO) should create one Entry Source for each messaging channel (email and SMS). This ensures that the journey can differentiate and respect the preferred communication method of each subscriber based on how they opted-in. Each entry source can then be used to trigger the appropriate welcome series content for the respective channel. Reference: Salesforce Marketing Cloud Documentation

 In Salesforce Marketing Cloud, once an email is approved using Content Builder Approvals, any subsequent changes require the approval to be withdrawn first. This ensures that any modifications are tracked and re-approved if necessary. By withdrawing the email approval, you can make the necessary changes and then resubmit the email for approval. Reference: Salesforce Marketing Cloud Documentation on Content Builder Approvals.

Contacts Analytics provides insights into the changes in the customer population over time, including metrics on new contacts, unsubscribes, and other population dynamics. This report allows marketers to track and analyze how their cross-channel customer base evolves, making it suitable for the marketing manager's needs. Salesforce Marketing Cloud documentation includes detailed information on generating and interpreting Contacts Analytics reports.