To me, most of the preseason games are glorified training matches and that's because most of these club players doesn't bring out the best from them when playing these preseason matches because the games aren't important to their respective clubs and the goals scored in the preseason games doesn't get added to a footballers record.
That being said, most of the English Premier League clubs has shown that they'll do extremely well when the new premier league season kicks in August
In pre-season matches, several teams did not appear with their core squad because the coach often tests young players to test their quality in pre-season matches. For several big teams they often provide opportunities for their academy players to show their skills in pre-season matches and often the coach finds young talent during pre-season matches which can provide an opportunity for them to make up for the main squad next season.
For now all the teams are having pre-season matches and for new players they can take this opportunity to adapt well to their new team in terms of their game. For Manchester United, we have seen their game which was quite interesting when Manchester United faced Arsenal where Manchester United were able to win this match. I think Manchester United strength in the next season will be even stronger after the signing made by Erik Ten Hag in this transfer window.