I think a major thing that needs to be clarified with all this. NHL.tv and ESPN+ were run by the same company: Disney Streaming Services. Because of that, NHL.tv isn't so much done with as it is being folded in to ESPN+. Basically, everything that was true about NHL.tv should be true about ESPN+, plus all the other content you'll get with ESPN+.
For your situation, in order to get every single game:
-With your ESPN+ subscription, you'll get all non-national out-of-market games plus all of the national games that are exclusive to ESPN+/Hulu. That will include every Rangers game that fits this criteria.
-You'll need something that includes regular ESPN, ABC, and TNT for any nationally broadcast Rangers games on those channels. Hulu Live TV will get you there, though there are other options (like Sling).
-You'll need something to stream MSG directly for any games against the Sabres that are not national games, because those will be blacked out on ESPN+.