I know a lot of people like the Toews comparison, but aside from size and position, I don't think they are all that similar, especially in their approach to the offensive game. He plays a much more pure skill game.
I've been saying it for a while, but Matthews' game with the puck on his stick reminds me much more of Patrick Kane. He's a bit bigger and not quite as slippery, but the hands, perimeter wrist shot, vision, dekes, composure, puck carrying, patience etc are all very Kane like. He goes to the net a bit harder than Kane did, but like Kane he relies more on fly by timing around the crease instead of setting up shop like a Toews.
And while he is a dangerous player from behind the net, I don't find him looking to set up there nearly as often as Toews or Kopitar. He seems to like the half wall and top of the circles much more. It's going to make him a very dangerous NHL scorer, as there aren't really many guys with his size and strength that can play that sort of skill possession game on the perimeter while still being able to dominate down low.