A strong character arc will weave its way through the turning points of the plot.
A character arc is the internal struggle and progress a character goes through over the course of a novel that changes them in some way. It's usually connected to the internal conflict so that what they do (the plot) forces changes in who they are (the character arc). It can sometimes be confused with character motivations (a character worries over something so they act to prevent that something) but why a character acts is different from how they change because of their actions. Motivation drives the actions. Growth is the result of the actions.
But should the writer know where the character is heading/motives before the first draft? Is it bad if you don’t?" Heck no.