For the most part it was ceremonial, but the Orders-in-Council were important for continuity of government. The use of the assorted Great Seals is required for official documents. The orders allow the continued use of the late Queen’s seals until replaced.
It was so fascinating to watch - the first time ever to see this type of transition as it happens historically. Very formal an the Brits do take this seriously. The crowds themselves testify this is important to them.