Amorim will still want a few more players to complete his squad before the official start of the competition. Bryan Mbeumo could be one of the good signings for Amorim, he will not need adjustments to the Premier League's tough competition. It's just that United still needs to bring in players, especially for the attacking sector, which I think Amorim is still not satisfied with the existing players.
I think the Portuguese manager knows he needs a finishing forward. That's why he might consider bringing in his former pupil, Swedish forward Gyökeres. If they sign him, they won't face any major problems going forward. However, Manchester United still has defensive issues. They need to strengthen their defense, and I don't see them making any major strides in that regard.
Unfortunately, Gyökeres seems to be more interested in moving to Arsenal. However, Arsenal provides something better than United. Amorim must get other options that can be done.
It is undeniable that United's defense will also make changes if it manages to bring in some new players. But if it is not a player with the best performance, United's performance will not be much different. Of course, it requires hard work from United to bring in the players Amorim wants, including the allocation of funds that may be difficult for United to agree on at this time.