The Organization has default Settings, and each Event has its own copy of Settings.  When you add a new Event, the new Event’s Settings are inherited from the Organization’s Settings, but can be tailored as needed for the Event.  When you copy an Event, the Settings for that event are also copied.  This means that Settings for any Event can be modified without affecting any other Event’s Settings or the Organization’s Settings.  Likewise, modifying the Organization Settings will not affect any existing Event.  A good practice is to modify the Organization’s Settings as needed early on, so that any new Events will have Settings tailored for the Organization.  This can reduce the amount of work required to set up a new event.