There are some changes you can make to a published tour, but some that require you to unpublish the tour and then republish.
If you need to make any changes to the constellation, you can do this by going back into "Build tour," make your changes and then simply click Publish again. You do not have to unpublish the tour. If you need to remove a panorama from your tour entirely, simply navigate to "Build tour" and remove the panorama from the constellation and click Publish.
If you need to make edits such as adding your nadir or blurring any images, you will have to unpublish the tour. These are changes that are appended directly to the images, which is why you must remove the tour to make these changes.