I agree with you. Copenhagen has already proved their mettle. And after watching Copenhagen's performance against Bayern Munich, I feel there is no way to underestimate this team. This team has the ability to be confident and perform well against bigger teams.
Manchester City's performance is still a bit shaky. Due to their weak midfield, the team is not getting the expected performance from Haaland in attack. So the Copenhagen vs Manchester City match is likely to be competitive. However, if Haaland and De Bruyne play well, it will be a little easier for Manchester City to dominate the match.
Despite Manchester City's dismal performance, I don't believe Copenhagen will have a chance to triumph over them. Because they want to return with their best effort and win the game, Manchester City is now ready for the encounter. They will provide a remedy to Copenhagen Man City only have problem with midfield. Other than that, I have no doubts about their ability to perform effectively throughout the game.
The level gap between Manchester City and Copenhagen is too great and there is no reason why Manchester City will have difficulty winning the round of 16. There is no chance for Copenhagen to put pressure on Manchester City, but at least they can put up a strong defense to quell any attacks from Manchester City. I think that's the only way if they want to play a draw against Manchester City, but if they concede first then Manchester City will not hesitate to destroy them with an unworthy score.
The return of Kevin De Bruyne to the main squad will be much more frightening for the Manchester City squad and I think that alone will make it even easier for Manchester City to score goals. Moreover, Kevin De Bruyne's accurate pass will be devoured wildly by their great striker Haaland.