If anyone read about or listened to Amorim's first press conference, it's pretty clear he has no intention of wavering from his preferred 3-4-2-1. "There is no second option". He might change his tune if United get tonked in his first 2-3 games but he sounds convincing for the moment.
Going to be really interesting to see if/how he fits Rashford, Garnacho, Dalot, Malacia, Mazraoui, and Antony into a team that will only use wingbacks going forward. I didn't list Shaw as he'll likely be a LCB at least until the next injury. And Amad has experience as a number 10. My guess is he's more likely to be used there rather than added to the wingback logjam. If I had to guess, I'd say this coaching change could be what ultimately forces Rashford out of United. No chance he's going to play as a wingback. He's not a 10 (even if he literally is). Is timeshare as a forward really in the best interest of Rashford and United?