Like many things in vim it depends on whether you wish to write it ;)
You can define your own popup(:h bexpr) however you feel, including per-filetype or buffer. Instead of simply operating on the variables it defines to you can also work upon the selection by querying the register(:h quotestar) instead.
As an example, I like displaying wordnet¹ popups when writing prose. Occasionally, I'll also dump diction² output in to a popup too.
However, I do think that using messages(:h :messages) might make more sense for selection info in general. That way you can select a text, call a map to display information, and still easily recall that data when you're in another place via :messages at a later time. Depends entirely on your use case, and once again how interested in writing the functionality you are.
