Power is probably the biggest enigma of analytics vs the eye test I've ever seen. I've watched entire games thinking that he's the worst player on the ice, and when I check the stats after the game he's sitting there leading the team in CF%, GF%, and xGF% by a large margin.
I've gone back and checked some of the shift charts, he seems to have the highest variance of shifts on the team. He'll get his tail kicked in one shift, then come back two shifts later and spend the entire time in the other team's zone. The analytics crowd will say at the end of the day all that matters is that he delivers positive metrics, but that's not necessarily true. For example, if he puts the team into a early hole, the later shifts that gets him into the positive may be good for his metrics, but too little too late for the overall team. For now all we can do is wait until he gets more experience and gets some more consistency to his game (which will mostly come with improvement in his own end).
As for his "physicality", I really don't care about his size and willingness to hit, cross check, or throw fists. What I would really like to see is a higher level of engagement/conviction from him. Tie up a stick or use your ass to box guys out, more often than not he's just not engaged, standing around puck watching. Having watched him in college, he's pretty much been the same player for 4 years now, so I'm not super hopeful that anything changes ( I know you've been saying this for a while too).
Sometimes it just seems like he's playing flag football while everyone else is playing tackle. I don't need him to be Pronger, but can he have the same level of engagement as other perimeter defensemen? Because right now he' just not hard to play against in his own end.