Avi Arad’s track record is a very mixed bag IMO. His films include the “Spider-Verse” films on one hand, on the other there is stuff like “Morbius” and the live-action “Ghost in the Shell”.
There is no doubt that Arad knows how to get the budget and bring the people together, but it certainly isn’t always working out as intended.
Depends, really. Producers do decide who will work on a movie in the first place. Producers’s biggest influence is during pre- and post-production. It’s true that producers stay out of the way during the actual production phase, but producers often take back control during the final cut (unless directors get the explicit right to do it that themselves) and other steps in post-production.