re: I am looking for showcase examples using
Sorry, I do not know of any live sites using this. Honestly, I do know if anyone is using it at all. I added it as a feature request many years ago. The maintenance of this specific shortcode option is from time to time I verify that it still works.
re: I am also looking for showcase examples where the showcase is built almost entirely out of the connections plugin
These sites make heavy use of Connections:
Not sure if that answers your question exactly :/
re: I am also looking for showcase examples of a simple list of the Titles in each listing in the directory so for example
No live examples, but there is a beta extension you can read about here:
Perhaps that will work???