Bayern is a very wealthy club with a very sound financial policy. Basically, they can keep any players they want. They also don't let players go easily. Lewandowsky did leave last season, but that must also have had to do with his age. They handled that reasonably well with Mane.
bayern didn't want to let Lewandowsky leave, Lewandowsky wanted to leave because from what I could understand the team wanted to hire haland to replace Lewandowsky and he didn't like that attitude from bayern and started campaigning to leave bayern as soon as possible, it wasn't a good attitude how bayern treated Lewandowsky. as for money, bayern has money and has been able to manage the players well, they have something very good, which is not constantly selling players and being harmed by such a sale
It doesn't matter who they play with, the B team is also so good that they easily become champions.
despite bayern being a strong team, they cannot underestimate the opponents, in the bundesliga if bayern played with team B they would not have any chance of being champions of the bundesliga, they would be relegated in my opinion, i say that because all teams in the Bundesliga are strong, it's not a place where you should play with a B team and expect a good result.