Pastrnak doesn't play a complete game at all, I don't know what people are talking about. His strengths are his shot and his ability to carry the puck up the ice on his own where he can beat the opposition one-on-one with his speed and skill. It's a bit hit and miss because he has that whole drunken master quality where he's in control when he doesn't quite look like he is, but by no means does this work all the time. Regardless, he's among the very best in the league at these two things.
He'll have some nice dishes that show up on highlight reels but he's by no means a great passer. He tries to force A LOT through. He's in a situation where he's given the freedom to be creative and risky with the defensive net of Bergeron in place. I think the redeeming quality for him is that he definitely tries and hustles when he doesn't have the puck.
If you're comparing that to Matthews, I think Matthews has arguably the best defensive stick in the league, it's just that his effort level is very questionable. I still think Matthews is more effective overall though.