I believe that impostor syndrome is a lack of overconfidence in one's abilities- that implies that you have the ability to assess competence and to assess the skills needed for a job or task, and you don't default to "I know I can do it well". When you encounter a novel job or task, you don't immediately assume competence, and you will remain uncertain until you fully understand the requirements of the job or task. A lot of impostor syndrome comes from "don't fully understand what's required, but it looked complicated from the outside", and will go away with greater understanding provided you actually have the skills and the competence to self-assess.
If you lacked the ability to assess competence in yourself, then you likely would not have impostor syndrome.
I don't see why it's a balance. Impostor syndrome typically lessens over time as you become familiar with the job/task and the requirements necessary to perform well, and are better able to assess your own skills against those requirements.
If impostor syndrome doesn't go away with time, maybe you are correctly assessing that you don't (yet) have the requisite skills.
If you never get impostor syndrome, then you either aren't challenging yourself or you might not have the subject area competence to assess your own skills level vs. the jobs/tasks you take on, e.g. Dunning-Kruger effect.