I think this will be a very good and uncertain match.
Both teams were very good in the first round of the group, but Bayern had a much stronger opponent, and at the same time showed great quality and dominance.
I think that Bayern found a very good replacement for Lewandowski in Mane, and they dominate again in the Champions League and in the German Championship and I give them a slight advantage in this match.
Barcelona also brought in new players and raised their level of play, and I believe that there is no chance that they will be eliminated in the group stage of the Champions League this season, as they were last season, although they are in a very difficult group of the Champions League.
Bayern is a lot more established club with most of their players, even though they lost Lewandowski, they got Mane instead and he is a great player as well, on top of that they also have players that could in return play very well and been playing together for a very long time as well.
Barcelona on the other hand got new players on all positions and there are only a few players coming back from last year, they do not have the chemistry that Bayern has, and neither way more talented than them neither. I am guessing Bayern will probably just run hard and tire out Barcelona and beat them by 70th or 75th minute, and score easier after that.
I think we both agree that Bayern is currently ahead of Barcelona, and in terms of game organization, experience, team cohesion etc.
Everyone wondered how Bayern would play without Lewandowski, but in fact, you can hardly see any difference in their game, they are still a great team, maybe even a better team compared to last season.
I watched their game against Inter and it was a rarely seen dominance from an away team against Inter in Milan.
Barcelona is slowly raising the level of their game with Xavi, but it will take them some time to reach the level of Bayern.