Best German island in North Sea to visit for a week

I'll bite because I am here. Only been to Langeoog. We are staying in Bensersiel and leaving in the morning. Langeoog was nice with a huge beach. We took the ferry there along with the island train to the town for the day. Pretty good tides here. Nice sunsets. Weather was hot the first few days, then cooler with rain, and now warming again. Norderney is perhaps the most famous island. You can rent bikes, but be prepared to pay the price. My opinion is there are nicer places than Bensersiel to stay, but things where fine here. We brought our own e-Bikes and road 20-50k a day. Flat, but with a headwind and cooler temps needed a jacket and a good e-boost sometimes. Moin moin...

Helgoland or Föhr. For what you want, probably Föhr.