To use the Einstein Engagement Scoring Dashboard for analyzing customer engagement:
Select Channels: Choose which channels (Email, Push, SMS) you want to include in the engagement scoring.
Activate: Click on "Activate" to start the data analysis process. This will generate insights based on the selected channels and customer interactions over the specified period.
Reference: Salesforce Marketing Cloud Einstein Engagement Scoring

Given that the customer's product catalog changes daily with products being added and removed, the import type that should be used is A. Overwrite. This import type will replace the existing data in the data extension with the new data from the CSV file each morning, ensuring that the data extension always reflects the most current product catalog without any outdated entries.
Reference: Salesforce Help - Import Types

For long-term success with Send Log data extension:
Data Retention: Implement a scoped retention policy to manage the size of the send log by periodically purging older entries. This prevents database overloads and maintains performance.
Custom Fields: Enhance the send log by adding custom fields not included in the default template. This customization allows for capturing specific data points relevant to NTO's needs.
Log Auditing Data: Ensure that all necessary attribute data for auditing communication effectiveness and compliance is logged. This includes variables like send context, subscriber responses, and engagement metrics.
Reference: Salesforce Marketing Cloud Send Logging

To avoid storing sensitive data in the cloud, the admin should use Tokenized Sending. This feature allows Marketing Cloud to send emails without storing sensitive data such as credit card numbers or social security numbers. Instead, Marketing Cloud uses tokens that are replaced with actual data at send time by an external system.