Four pages. The first lists what the platform does for a server-rendered site without code of yours, and it is meant to be complete, because the list is the argument; it also says in one paragraph why Smarty or Twig is a separate decision. The second is about in-context editing, the item teams undervalue most. The third is the cost, with the precise reason one personal element can make a whole page uncacheable. The last names the two signals that server-side rendering is the wrong shape.
Read the cost page before writing the first template. It is what makes the next unit, on hybrid builds, necessary.