Can I change the privacy setting after the event is over?

Yes, at any time, and it takes effect immediately for everyone including people who already have the link.

Yes. A common pattern is to run the event as protected so guests can join easily, then switch it to private a week later once everyone has looked, or to public if you are happy for it to be shared onward.

The change applies at once. Someone who had the gallery open in a tab loses access as soon as they reload or scroll for more photos — access is checked on every request, not once at the start.

Going private does not delete anything. Your photos, the archive and the keepsakes are unaffected; they simply stop being visible to anyone who has not joined the event with its access code.