Amorim seems to understand Manchester United weaknesses very well, he has evaluated the players when under Erik Ten Hag guidance. In front of the Media Amorim has explained that being a Manchester United coach is a tough job so he doesn't care about people who doubt his quality, Amorim only wants to focus on his target to return the players to their proper positions.
I am sure that before Amorim really handled Man United, he had previously studied and had a little idea about the team he would handle. After Amorim officially became the head coach, he then made an approach and maybe as you said, that Amorim may really understand the weaknesses of the Manchester United squad. but it is clear that only understanding does not necessarily mean that he can fix United in the shortest possible time, what is certain is that he will need time, especially if Amorim changes the system according to his program. I also read from Fabrizio Romano's report, it seems that Amorim will often rotate or shift some of his players. I tried to interpret it, it is very likely that Amorim will apply the same system as when he handled Sporting. if so, Amorim will shift some of his players or maybe he already has a line-up of players who are his main starters. so, don't be surprised if maybe some of the main players who are usually in the starting eleven become reserve players under Amorim's guidance. well, tomorrow's match against Ipswich will be his debut as well as measuring how effective the tactics and systems he applies are. related to the team squad, there is no choice for now, he only maximizes the available players. It could be, if Amorim wants some new players in the next transfer window.