I think I might have the wrong idea on lines so correct me where needed.
Line 1 is your best offensive threat. Average defensively.
Line 2 is you second offensive threat with the ability to defend longer stints in the D Zone.
Line 3 is who you put against the other team’s first line. Defensively minded with some offensive ability.
Line 4 plays against the other team’s fourth line. Little offensive threat and average defensively.
The more I think about it you want at least three lines who can score and everyone playing a two way game. I remember the chances of a fight came when those fourth liners were playing their five minutes of ice time per game.