Please refer to 5.2 and 5.3 of Guidelines and Standards for Tactile Graphics in order to understand the various scenarios for print and/or transcriber-assigned headings. In the examples you have listed, you haven't said whether or not there is a heading in print. If there is not a heading in print, one would not be added before the caption or key. If the caption prepares the reader for what they will encounter on the tactile, it is not necessary to assign a heading (unless this is a decision that has been made by the agency for which you are preparing tactiles). Only where the graphic extends beyond one page, does it become necessary to add a transcriber-assigned heading. This is often done to clarify which part of the graphic is being viewed when it has been necessary to split the graphic into layers or sections of information. The same is true when there is more than one key (i.e. a key for part 1 and a second key for part 2)--see page 5-29 through 5-31 of the Guidelines. The heading "European Union" has been taken from the print legend. On page 5-31 is is placed [u]after[/u] the caption.
Note also that although Braille Formats would insert TN symbols around anything added by the transcriber, this practise is [u]not[/u] followed for headings or explanitory labels added to a tactile graphic.
Each situation must be studied carefully and the guidelines applied based on the purpose of the graphic and how to present it clearly and concisely. There often is not only one 'right' method, so strive to find the 'best' for a particular graphic.
Hope this helps,