Do I need 12 testers for every app?

Yes — the requirement is tied to the app's package name (its unique Play Store identifier, like com.yourcompany.yourapp), not to your developer account as a whole. A second app is a separate application submission to Google Play, package name and all, and it goes through production-access review on its own.

This is why every Testers14 order is scoped to exactly one app: the package name you paste into your dashboard's setup wizard is what your testers actually opt into on Play Console, and it's the identifier Google checks the 12-tester/14-day count against for that specific submission.

Publishing three apps under one developer account means three separate closed tests, one per package name — not one test that covers the account. If you're planning multiple apps, each needs its own order and its own testers.