How do I set my entity type — LLC, S-corp, sole proprietor?

Entity type changes the tax math, not just a label. After you save a new one, a notice says your tax estimates have been recalculated and suggests checking with your CPA if you already made payments based on the old type. The estimate treats the whole year as the entity you pick, so it does not split a year around a mid-year S-corp election — check that with your CPA.