I'd start read-only for a week or two. Pull search terms, ask why CPA moved, see which campaigns eat the budget. You find out fast whether the assistant reads the account the way you do. Once it does, give it write access for one narrow job, like adding a batch of negatives you've already reviewed.
The argument for going straight to changes is that the preview step already protects you, so waiting feels slow. I don't think that holds up. A preview only shows what the model proposes, not whether it understood the account's history, and that's the part that bites you. It can look perfectly reasonable and still be wrong because it didn't know about last quarter's restructure or why a campaign was paused.
How do you sequence it when you're running more than one platform?