I wonder if it’s OK to switch temporarily (for some kind of event) my survival server to adventure and then back. Wouldn’t it despawn some things or maybe break villagers or something like that?
Don’t see why it would cause any issues. Obviously you won’t be able to interact in the same way but don’t see why it would despawn anything.
Gamemodes are player settings so they shouldn’t touch your world at all.
for example peaceful mode will despawn hostile mobs, even if you named them…