Boundary skills are a moving target because there’s no one right way to do it. There’s no perfect script to follow to get everyone to play along nicely. Boundaries are hard! They’re hard to recognize until crossed, hard to talk about, and especially hard to give someone consequences for crossing them. You will spend a lifetime learning about them and still mess up sometimes. That’s ok; you’re human.
A narcissist sees people as objects to move around the chess board of life. To make this easier, the narcissist classifies people into status (high to low) and usefulness (high to low). Generally, as a person, you don’t like being a chess piece. To the narcissist, its efficiency.