Actually it can better for Kane's career in terms of titles if he joins Bayern Munich instead of Manchester United. Because I think it is obvious already. Manchester United aren't a team that win even the Premier League title often. They can't guarantee anything about this for Kane as a result. Because it is already very difficult to compete with Manchester City for the title and now Arsenal are also much stronger. We don't even know how much Erik ten Hag can make an improvement in their success in the long run.
But if Kane signs for Bayern Munich then it is like it is nearly guaranteed that he will become champion in the Bundesliga every season. In addition to that the team can be much more competitive for the Champions League title as well. Because Kane can make a similar impact to Lewandowski for them.