Personally, I see him as a winger. I know Colt mentioned he doesn't think he wins enough board battles to play wing but IMO, being strong along the walls and winning battles is more of a center thing now with the way the game has evolved. C's have to help win battles down low. Every once in a while there will be a puck up the wall on a breakout that the wing has to battle for but most times that puck is one-touched to the C/back to the D or chipped off the glass and out. And ever since they changed their breakout two years ago, the wings are asked to stretch the D by leaving the zone early so they can pick up indirect passes off the walls and glass. They're the guys who carry into the offensive zone now, not the centers. In the offensive zone, forward positions are meaningless. It's about motion, cycles and switches, moving pucks low to high and side to side.
So IMO, speed has become more important than size on the wing.
Fwiw, I think the whole RW/C thing is one of the issues holding him back. I think the B's see him as a center, and he's a bit undersized for that job. But because they "like him at center" they're very slow to consider him at wing. It's like Backes. They "liked" him at wing, and it's taken catastrophic injuries for them to even consider him at C.