Dont understand how hooks and arcs are supposed to work in Masks.

I understand what the book lays out - arcs are the villains going after what they want harder and harder, and hooks are trying to work out which of a pair of labels the PC prefers but phases and impulses confuse me.

like the book lists that mundane vs saviour is about "protecting people from threats both outer and inner" - is it always that? What about trying to get a PC to pick between their responsibilities as a civilian (their friends, their parents) or their responsibilities as a hero. That doesnt match up with what the book says mundane vs saviour is, but is still about which of the labels the PC sees themselves as.

And for phases I dont get how often I should be incorporating stuff from each phase? How do I know when to move from one phase ot another? What happens when one villain isnt featured for several sessions - are they in a different phase to one who has been getting featured? With my current understanding of them, forcing in stuff from phases in feels considerably less collaborative then I generally run PBTA as.