Is adding QR & ID to the Certificates optional?

Yes. Adding a Certificate ID and QR code to your certificates is completely optional.

Multiple Certificates Pro works fully without them. You can still,

Assign multiple certificates to courses, groups, quizzes, and lessons
Email certificates to students upon completion
Save certificates to the server
Let students view and download certificates from the My Account page or via the shortcode

The Certificate ID and QR code features are only used when you choose to add them.