How does the content plan decide what to create?

The plan already knows everything on your site, and it ranks the whole job by impact.

Where you're missing a page that matters, it creates one. Where an existing page is worth saving, it refreshes it on the same URL, so you keep the legacy value. It works through both in priority order, biggest bang for your buck first.

You don't need to work out which pages to keep or what to write next. The plan has already done it. And if a suggested item doesn't fit your practice, mark it "Not relevant" and the plan reshapes around your feedback.