For information on the westward shift, it is found in the section called Forecast Discussion.
For Forecast Discussion 11, it’s in paragraph 2, where it talks about the changes in the forecast tract.
There has been a westward shift in the model guidance
overnight, perhaps due to the trough tugging Idalia more
northward before taking a north-northeast turn. It should be
noted that the ECMWF ensemble shows many of its strongest members
on the eastern side of its guidance envelope, which is a
reasonable place to be given the synoptic pattern. The new NHC
forecast is adjusted a little to the west but is now east of the
model consensus on the eastern side of the reliable model guidance.
The Public Advisory has information on the radius of the hurricane and the tropical force winds.
That gives you a rough diameter around the track that you can possibly have winds of this force or highter (as the winds get more intense the closer you get to the core).
Currently, this is in the section DISCUSSION AND OUTLOOK, where it says
Hurricane-force winds extend outward up to 15 miles (30 km) from
the center and tropical-storm-force winds extend outward up to 160
miles (260 km).
The diameter is actually asymetric, so this is okay for a rough guess.
The Storm Surge section gives you the potential area and surge you might expect.