Reviewing opens and clicks activity summaries is the best action to evaluate journey performance, as it provides information about how subscribers are engaging with the emails sent from the journey. The activity summaries show metrics such as unique opens, unique clicks, unsubscribes, bounces, and complaints for each email activity in the journey. These metrics can help the marketer assess the effectiveness of the email content, design, and timing.

Removing the bounced addresses before the next send is a best practice to uphold the sender reputation and avoid being marked as spam. Bounce rates above 10% are considered high and can negatively affect the deliverability and engagement of email campaigns. [Source: Trailhead]

If you import an encrypted file of subscriber data, you need to configure Field-Level Encryption in the import file activity. This allows you to specify which fields are encrypted and how to decrypt them. The Manage Files in File Transfer activity is used to move files from one location to another, not to import them. The character encoding setting is used to ensure the correct display of characters in different languages, not to decrypt encrypted data. You can learn more about this in the Importing Data into Marketing Cloud module on Trailhead.