I both agree and disagree with some points here. On huge events like the Super Bowl you are 100% correct that the goal is to funnel as much money through the book and collect the 10% juice. Sportsbooks are now starting to take more proactive stances on games where they think they know the right side and are willing to lay a line that draws in lopsided action and are willing to play the percentages that they'll come out ahead. Books also know more often than not which side is going to be the public side and will skew the juice/line that way to make people pay a premium. You are also correct that the initial linesmakers are worth their weight in gold. I'm not sure if this is still the case as they've exited the US market but the book at Pinnacle used to be the gold standard and had the sharpest line/juice anywhere and I heard that lots of other books would simply copy Pinny's line moves.
Here's a fun article that talks a bit about the line making process.
https://www.sportsinsights.com/betting-tools/sportsbook-profit-margins/
As for the NU line, I agree with Severe that it probably ends up around -3. It would take a mountain of one sided money/key injury to move it past that key number.