When signer uses 'Assign to Someone Else', who gets the executed copy? The original person asked to sign, the person they assigned to, or both?

Based on DocuSign article information...the Original Recipient will be set as Carbon Copy so they should get a final document email.

When a recipient receives the document, they select the Assign to Someone Else option. The recipient provides the new signer's contact information, and the document is reassigned. In the document, field tags for the original recipient are reassigned to the new signer. The new signer receives a signing notification, which includes a message from the original signer if they opted to include one. The sender receives a change in signer notification. The original signer is added as a carbon copy recipient.

Once the document completes, the Certificate of Completion reflects the details of the signing event. The new signer is shown in the Signer Events section, and the original recipient is listed under Carbon Copy Events.

Here is the specific article...https://support.docusign.com/en/guides/ndse-user-guide-set-advanced-document-options