I am an INFP. I seriously thought they were both INFP.
I agree with the previous post that Dave's full of what-ifs. John sounds introverted, but he has to do something to be a performer.
In my opinion, an ISFP artist is more on the practicalities of life. INFPs complicate things, like creating issues & conflicts.
I know lots of ISFPs and although, there are similarities, I find them practical and less dramatic than INFPs. They are good with what's visible. INFPs are good with situations and ideas, only in their heads. Taylor Swift to me is an ISFP, her message is light. When it's emotionally heavy, I think it's INFP. ---> Just my opinion.
John Meyer is NOT a Fi-dom. His demeanor, things he says, etc, have no relation to any Fi-dom description I've ever read. I'd say Se-dom, ESTP, honestly (why do people think he is a feeling type?). In any case, an ExxP type.
I can buy Dave Matthews as ISFP.
"Charlotte sometimes dreams a wall around herself. But it's always with love - So much love it looks like everything else. Charlotte Sometimes - So far away, glass sealed and pretty." - The Cure