Email to Case Premium:

• The "Display Existing Files From" setting determines whether Attachments, Files, or Both Attachments & Files should display in the existing section under attachments on the New Comment page.
• The "Insert New Inbound Files" setting allows administrators to determine whether incoming attachments should be added as Files or Attachments.
• The "Insert New Outbound File As" setting determines which object new email attachments on the New Comment page will be inserted into, either Attachments or Files.

File Slayer:

• Files are supported out of the box, and Attachment support has been retired starting in version 5.16. 

Case Merge Premium:

• Files is an option to be selected under Standard Objects in the Child Objects settings tab, allowing Files to be included in merge operations.

Case Flags:

• The "Set Flag on Case File" setting controls whether files added through community portals should flag the case.

Case Split:

• Files are automatically included on the Split page, with no special configuration required. Administrators can choose to delete the original file from the Case Split setup wizard.

For more information on the Files object and this change Salesforce is making, please see the following additional resources:

• Compare Files and Attachments features
• Lightning Experience: Attachments are being replaced by Files and not returned in search
• Why You Should Add the Files Related List to Your Page Layouts
• Considerations for Using Files and Attachments
• Using Salesforce Files