If you delete a Package from your Settings, existing Bookings the Package has been used on along with any associated Menu Items, Events, and Invoices will not be affected.
If you delete a Package from within a Booking, the Package will be deleted, however, all associated items will remain on the Booking without the Package features.
Prefer Archiving?
For better record-keeping, consider archiving packages instead of deleting. Deletion should only be used for test packages or accidental creations.