TestFlight external testers' upgrade workflow after app is released to App Store

Question

When releasing to the App Store after using iTunes Connect Testflight beta testing, what's a good way to ensure that external testers get cleanly upgraded to the official App Store version? Specifically:

• Will external testers get a notification on the device that a new app version is available? Will this be a regular iOS notification, a notification from the Testflight app, or both?
• On the home screen, will the beta app's icon show any indication that it's been superseded by a non-beta app?
• If the user has automatic app updates enabled, will the app store app download and install automatically, replacing the beta app? Or will the user have to upgrade manually even if auto-upgrades are enabled?
• If the user opens the Apple Testflight app, will they see any indication that the build they were testing has been superseded by a released build?

If the answers to some of the above questions are "maybe" then what configuration or settings should we use to ensure that app updates work as expected? (where "expected" means that when we release the app to the app store, then all testers should be updated with that new version of the app).

Googling on this topic hasn't been very helpful, perhaps because Apple's TestFlight support is only a few months old so Google is dominated by non-technical news links instead of technical blogs and other places that may offer more details. I've been unable to find any programmer blogs which talk about the "upgrade from external tester to app store version" workflow.

Apple's documentation is clear about what happens from the perspective of the iTunes Connect web application (see excerpts below, coalesced for clarity) but not very clear about the external testers' user experience, which is what I'm trying to figure out. Here's excerpts from Apple's Docs illustrating this:

Finish Testing an App. To stop testing a prerelease version of an app that is actively being tested in TestFlight beta testing, set the Testing switch into the Off (white) position.

提交到App Store完成TestFlight beta测试后,您可以提交应用程序进行最终审核.在提交之前,请确保您不再需要测试它或之前上传的任何版本.当应用程序在App Store中变为Ready for Sale时,测试会在早期版本中自动停止,您将无法查看或测试它们.请参阅何时构建变得不可用以获取更多详 如果要继续测试早期版本,可以将其作为与新版本预发布版本关联的新版本上载.

When builds become unavailable Before your app becomes Ready for Sale, the Prerelease pane lists all builds for all prerelease versions you have uploaded. After the app becomes Ready for Sale, some of the builds will be removed from the pane:

The build used in the app is removed from Prerelease, as are all other builds in the same prerelease version. All builds in earlier prerelease versions are also removed from Prerelease. On the Prerelease page, the sections for those prerelease versions will be removed.