With Apple you can manually choose when to publish the updated build after it has been approved. You can read more about this here. Knowing this, you would be able to push your snapshot to live to coincide with the build going up on the store to minimize downtime.

If you want to change some attributes of your game in a new build release, you will need to update the build because the client side of the game would need to be updated to include the new event attribute. If you had the game's configuration in Meta Collections, you could update these on GameSparks and publish a new snapshot without the client needing to update the build.