Not sure about Barcelona and PSG will be there until the final stage, especially about Barcelona which seems like Barcelona's performance will still not be much different from the results they got in the previous season too. But for Manchester City, of course I personally still believe Pep Guardiola still has a very good ability to make Manchester City go further. Also about Manchester United, although the chance to get the title is very low but at least Manchester United has a good chance to get to the quarter-finals, maybe.
There is no much difference in the squad Barcelona used last season so i am not expecting any changes or extraordinary performance from them in the champions league. If they are able to make it through the group stage I don’t think they will go past the round of 16 because they didn’t really add much to their squad. Football cannot be predicted sometimes but I really think it would be difficult for Barcelona to pull unexpected stunts.
PSG and Manchester United on the other hand can go further in the competition maybe the quarterfinals or semi final but I don’t think they can do better than that next season. PSG has some good players enough to win the champions league but I don’t know why they end up losing everytime even having a player like mbappe. Manchester city are ambitious enough to win it again but it will be very challenging for them to do it over again this coming season.
Sometimes league matches can be forgiving. Because there are good chances for a better team to improve later. But Champions League can be a problem. Because it is really hard for any club to actually improve quickly in the Champions League after they get themselves in some problems earlier on in the competition.
I don’t really understand your point here but sometimes a team might have a bad performance in their domestic league and still perform wonderfully well in the champions league take inter milan last season’s performance as an example, they didn’t perform too well in serie A but suprised the world in the champions league. Some teams may perform well in the league but fail to perform in the champions league just like barcelona did last season.