Bruno Fernandes fired United to a 2-0 lead before Jarrod Bowen pulled a goal back for West Ham.
After the 2-1 win, Amorim said: "It was completely different to last season. We didn't suffer, we scored and that can help you play better. We had some possession, we defend well, one against one, we press high, especially the goal-kicks and it helped us to win the ball sometimes.
"I think we need to have more long possession when we win the ball, so that we are near the box and try to find the small spaces. We can handle the ball and work the ball a little bit more.
"Until the West Ham goal, we were controlling the game, with more opportunities, and then we suffered a little bit, we changed all the team with a lot of young kids. But it was a good test to improve the team."
On who impressed, Amorim also said: "All the guys. I don't want to talk specifically. Rasmus (Hojlund) did well. I really liked Rasmus's game, the runs and the way he fought during the game, one against one, when we kicked the ball.
"He connected with the team-mates so he did a great job, Matheus Cunha is that kind of player that can help us, he can help us a lot because he can run with the ball and that is something that can change the game. We missed that last year. In the first half, Kobbie (Mainoo) and Manu (Ugarte) were really good.
"I'm not going to talk about the second team because it's really hard for 11 (10) players to go to the pitch, you know, a lot of young kids. But I really like the team. Of course, you have to look at the game and you have to improve things."