I think Bayern Munich has a better chance of winning, and as for the reason, their defense is stronger than last year. They also have very high-quality players who know how to play in their attacking lines. Especially Harry Kane is a great goal weapon for Bayern Munich. Barcelona should do their best to stop this. If they can't do that, Harry can punish them. This match will definitely be one of the most interesting matches of the upcoming matches.
In the Bundesliga, RB Leipzig and Union Berlin have the best defence based on the number of goals they have conceded. The former have been scored just two times and the latter conceded just four. Bayern Munich's defence might be better this season compared to last season, but they still have not gotten the best defence. Taking in seven goals in six games doesn't show that the defence is solid.
Harry Kane is gradually reinventing himself, and you are correct that he can punish Barcelona if they make any defensive error. The games with VfB Stuttgart is very important to the motivation of the players before the UCL match. If they can defeat Stuttgart, I will serve as a motivational tool to deal with Barcelona.
I think the Stuttgart match to be played in Munich Arena will end with Bayern Munich's victory. Because Bayern Munich does not lose easily in their own field. Also, their situation this year is better than last year. However, I agree with you that they conceded too many goals. The technical director has probably identified the deficiencies since he was a player in the defense zone when he was a football player in the past. He will definitely request transfers to those areas during the mid-season transfer period.