5-on-5 goal differential, or in other words: winning.
The game is about scoring more than your opponent. If you look all the 4 seasons, regular & post season, Laine is third after Scheifele & Ehlers. Also, if you take out his very bad 18-19 season, Laine actually leads the 5-on-5 goal differential.
Everything other is interesting and all, but positive goal differential wins you the games.
From top of my head, last season Laine&Scheifele were together 5-on-5 +38 - 33 = +5. Not super cool but still good. I don't think you should play CSL together, but it did work OK.
Last season Wheeler&Scheifele reunited for +18 - 16 = +2. Slighlty worse, but still winning, which has not been the case always for CSW that tends to cause a lot of offense on both ends of the rink. These stats can't pick up those occasions where eg. Wheeler jumps into the bench after being too deep into the o-zone and the opposite team scores from odd man rush. But nevertheless, 5-on-5 goal differential tells you pretty much, when the sample size is large enough.