I don't think either player had much of a marginal impact on their team's destinies, they probably would have been in the same place either way.
Nashville had a good team in 2016, they lost in the 2nd round in game 7 to the West champs. Their biggest downfall was weak goaltending from Rinne. That team had some improvements up front, and most importantly got like .940 goaltending from Rinne who played his best in 5 years through the first 3 rounds. That carried them to the final.
For Montreal they ran into a bad matchup against a hot Lunquvist and a tight checking Rangers team. They didn't have the offensive talent to breakthrough. Could PK been a bit more helpful? Maybe but Weber was IMO the 2nd most effective skater for the Canadiens after Radulov so he really would have had to put on some Karlsson-esque performance to do improve on Weber (which he never really did on Nashville). Weber also rang the post like 2-3 times on big clappers that had beaten Lunqvist, an inch or two could have swapped a game or two.