I can’t speak for the NHL side as have never been to a game, though have a bit of experience of the North East cities you mention – in order of least liked!
Boston – nice to look at but found it a little anti Brit!
Phili – found it quite friendly – much more big city atmosphere but still a lot to see
Montreal – daughter did a year at Concordia uni and visited the place a couple of times – thought it was fantastic – as stated majority speak French though didn’t meet anyone who didn’t speak English also.
all ime/imo etc..
might want to consider Toronto also – really enjoyed there also and has easy access to the other N/E cities you mentioned (to make a trip of it)