Manchester United deserve it with their performance, they were the better side in this series and we have to congratulate them but can they still bring this very performance, this same energy to the EPL when next campaign begins? In as much as they played against same EPL clubs and won all 3 games I still find it hard to believe that they can replicate same display or even more when it matters, it won't be like we saw, but can Manchester United start the season with a win?
Nevertheless, you can't really put PL summer to benchmark their performance in PL. This obviously all of teams are playing more seriously in the main league instead of friendlies.
As for their first game, I don't think they can win against Arsenal. It's probably they lost it.