All our managers have had 'final say'. That does not mean they have always got close to their first choices. I feel confident saying there is a list with preferences in order, that list is evaluated by the committee, and the edited/updated options are presented to the manager. Even Conte would've had to 'allow' the Spence signing, doubtless with the caveat that he was in no way obliged to pick him or play him. As has been said many times, the club had a method and agenda moving forward which centered around a specific type of recruitment. So by proxy, the manager is working with a committee plan.
Again, it is my view that you (and others) won't have to worry about these sorts of things for the coming season anyway as I believe he will not be retained...