I haven't watched them enough to comment with much insight. But, I do think San Jose's PP this year will be a great test for the theory that teams should pretty much always run a 4F-1D PP. Nashville is the team that does it the most, and they are generally a middle of the pack PP team. Most of the ones that have been elite over the past couple years run a 4f-1d set up like Pitt, Toronto, Tampa, Washington, and Tampa who are the top 5 PP's in the NHL during the 2016-17 and 2017-18 seasons when combined.
Nashville is one of the only teams that I can think of that constantly runs the 3f-2d set-up, and despite having elite talent, are only the 12th best PP over the past 2 years (11 if you remove Vegas).
Now, Karlsson and Burns are arguably the two best offensive defencemen in the league (it might not be much of an argument). So it will be interesting to see how this PP does, and whether it can be a top 5 or top 10 unit. Now, I know PP's can be erratic, so its a bit unfair to go off of one-season of data and draw too much of a conclusion, but I do think it has some interest as a test case.