I know this is a basic question. This is the first time I have used a personalized Touring Plan and the first time we have been since FP+. I had a good feel for how long stuff took in the paper FP era, but this is a new day.
So I have made personalized plans for our trip next week, and they of course have very specific times for waits and walk times. How accurate can we expect them to be?
In my experience they have been very accurate overall - some attractions were longer and others were shorter, but the total for the day was very close.
Bear in mind that any number of things can throw the predictions off, so it is always good to mark things as Done on your plan and re-optimize if you start to go significantly off-schedule - this way the Optimizer will come up with the best possible plan for the remaining attractions given the current conditions.