With such a strong opponent, a defensive strategy might be the best choice for Schalke, and at any time they can take advantage of Bayern Munich's mistakes to carry out a quick counterattack. I know very well that defensive strategies have a lot of risks, because if they are pressed continuously they will tire more quickly, and when fatigue starts to get in the way, it will result in decreased concentration. And in the defensive strategy they have to be able to maintain concentration, maybe that will be an additional job for a coach.
Meanwhile, clubs that play offensively will usually leave gaps in the defense, and Schalke can take advantage of that, and at times like that they are required to play effectively when they have opportunities.
They can try whatever, it is not going to work, Schalke is Schalke, even though they got better recently, they are still much worse and no matter what they try, the end result will be the same and they are going to end up with a loss. It's fine though, they are already out of relegation zone and how hard it could be to expect teams that low to lose at the same week as well? Stutgart losing to Leverkusen, Bochum losing to Augsburg and Berlin losing to Köln.
All of those are very likely results and should happen if you ask me. I think it is important to realize that we should not be focusing on anything that will change the end result too much, just Schalke losing and all others losing as well. If not, they will have to fight harder for the rest of the season.