Here are a plain list of modules that really gives site builders front and backend super powers and make these two categories of developers closer than ever.
It supports the creation of new pages, and allows placing blocks within that page.
Like Drupal 7's Page Manager, it provides a concept of "page variants", each with their own selection conditions.
Additionally, it can be used to take over an existing page, like overriding
/node/% to change what is displayed when viewing a node.