In your version of Sage 100 you don't need to setup each customer to email the salesperson.  You can set that up in Salesperson Maintenance.  When in Salesperson Maintenance with that salesperson number being edited, click the Paperless button you can then choose which documents that salesperson should be emailed when their customers are sent an email.

Is that the case even if Paperless Delivery is not turned on for the customer?

No, the customer would need to be setup for Paperless Office.  The setup in Salesperson Maintenance eliminates the need to go to each of the customers and add the salesperson email.

In the 2021 release there is a new Default Delivery Options maintenance task that allows for pushing the Paperless Office setups to customers and vendors.

What would be the best method to globally change all of the customers, for that particular sales person to Paperless Delivery for S/O and S/O Invoice?

Edit!!  As BShockley notes below the V/I import is possible.

Unfortunately V/I is not available for the tables, AR_CustomerDocuments and AR_CustomerDocumentContacts, that store the Paperless Office delivery options for customers.

Where is the Default Delivery Options located?

That was just introduced in the 2021 release.  It is in the Setup menu for the Paperless Office module.

I have imported paperless office data into these tables in the past.

You are absolutely correct, I am sorry that I didn't look at that closer before posting.  I was confusing the lack of V/I import to some of the P/L tables such as the log tables.  AR_CustomerDocuments and AR_CustomerDocumentContacts can be used for V/I imports.

Once the AR_CustomerDocuments records are imported, then the setup can be done in Salesperson Maintenance so that importing the salesperson email as an additional email in AR_CustomerDocumentContacts would not be necessary..