In the early stages the Project Manager creates a high level plan based on outline requirements and a high level view of the solution.
From there on the end product is created iteratively & incrementally. Each increment building on the output of previous increments. At the end of each stage, the outcome of that stage & experiences gained are to create a detailed plan for the next stage.
Detailed plans are created by team members, Not the Project Manager!
Within each stage the works in close collaboration with the business/customer to understand the detail of the next step to create and validate the evolving solution.
For the Project Manager, the old ‘command & control’ is replaced by a facilitative approach.
The Project Manager focuses on management of an empowered team, ensuring they have all they need to deliver, only stepping in when an exception is escalated from the team.