Question about WORM and encryption

Hello all. I'm currently writing a report for a class in my cybersecurity bachelor's degree program. I want to protect the offsite backup of Company X's data, ensuring it's both immutable but also protected from unauthorized access. I'm suggesting write once, read many. I understand the concept of WORM, but I have a few questions. Data protected with WORM can be encrypted prior to being saved, correct? It just can't be encrypted AFTER? Is WO