Germany has 17 DPAs, each covering a region. Plus there is a federal DPA, apparently. Where do complaints go on cross-border situations?

(crossposted from !gdpr)

Where should an Article 77 GDPR complaint be sent when a cross-border scenario involves a data subject outside of Germany?

Do data subjects have a choice between the federal agency and the regional?

I could not find any PDF forms for art.77 complaints in Germany. Do they exist?

The list of agencies is on this page:

https://www.datenschutzkonferenz-online.de/datenschutzaufsichtsbehoerden.html