Group node from OG membership doesn't work
Solved it. The panel needed the relationship. This can be added on the contexts-page of the panel. The relation I added was:
 Node from Node (on Node: Groups audience [og_group_ref])

When this is added it can be chosen instead of "This node" when Views panes are added to a page-layout. 

This works with the default OG Content-view with the relation OG membership: Group Node from OG membership added to it. (on groups without content this gives No content in this group however.)