How Much Autonomy Does the Fed Chief Have in Formulating Doctrine

The entire world will specifically be tuned into the speech that jerome powell is scheduled to give at the conference itself. I mean, markets pretty much are guaranteed to move in response to his choice of words. And that got me wondering about how do powell's speeches get written in the first place,. I mean, how much autonomy does the fed chief have in deciding how to describe what the banks policy is?