Vigneault has done a good job with systems, but yes a big thing is that Canada selected appropriate defencemen. There isn't a Demers or Edmundson this year to muck things up because he's so ill suited to the larger ice surface. Heady defencemen with good skating, particularly young defencemen, should be Canada's targets for this tournament. It's good to get these guys reps in the (hopeful) event that there is a bigger tournament waiting somewhere down the line.
Regarding the hitting, that is a part of Canada's game that is missing and probably should be brought back but it's out of style at the moment. You can see flashes in guys like Dubois or Mantha, but they would have been physical monsters had they come up 15-20 years ago. One good element of Canada's game that has been big in this tournament is that the team has been tenacious when trailing. In the Summit Series it was noted that the opposition found it odd that the Canadians kept playing very hard even when the game seemed over. That is still there at least this year.