I've been slowly adding to the FAQ page on the wiki [1]. Please feel free to add/change what's there. It's good if you can also add labels at the bottom of the page, as that can make searching work better. Please also consider listing any tickets that would fix things addressed and reference the version they will be fixed in. That way, someone using an older version will have options/guidance. I hope this is a helpful resource.
-Jenn [1] https://cwiki.apache.org/confluence/display/NIFI/FAQs