I have watched JV quite a bit since he 14. His defense is not great, think Kassian, but his offensive upside and tools make him a dynamic, think a tuned down Neely.
He absolutely could be the best power forward in the game someday, but he will never lead in plus/minus.
He shoots first, skates first, hits first, scores first and then looks to pass and back check. With the right center,think Hull and Oates, he could pot 50.
His defense will need a lot of work and could get him benched. His hockey IQ is likely okay, his offensive IQ is high. The first time he steam rolls someone in Vancouver it will be love forever. He was destroying kids (physically) 4 years older than him when he was 14.