How to properly add publisher accounts to TestFlight?

Question

iOS

Began negotiations with the publisher about his application. The publisher asks to publish the build through TestFlight, sent a pack of e-mail accounts for him.
This is my first time with this system. The build seems to have been uploaded to the system via iTunes Connect.
Do I understand correctly that publisher accounts need to be added to the list of external testers?
So they won't get notified until apple approves my app?
Or am I wrong and should I add them to the list of internal testers? Internal - the notification comes to the mail immediately, without approving the application by apple.
It's just that the application is currently raw and there are big doubts that it will pass the approval ... And why is it needed for testing?
Well, who came across, tell me - how long does it take to approve an application for testing.

Answer 1

Submit for approval for beta testing, the review is very fast, it's not for the AppStore after all, you won't lose anything. Accounts for external testers.