On paper, Manchester City can be seen as the biggest favourite for the Champions League title. In the end, they have a more completed squad at the moment. Haaland's arrival will help them become closer to the title compared to the previous season. But we need to see their performance against the other big favourites as well.
For example, their elimination by Real Madrid last season was really dramatic. It was like they were so close to making it but Real Madrid performed a miracle in the last minutes of the rematch. Guardiola needs to focus on getting his players well-prepared for this kind of matches this time.
The Champions league is one of the toughest league to predict who will win it. Manchester City has the qualities to win the league, their are other league that are well fit to win it too . So it is something that you can't really tell right now.