It could be said that with Bayern Munich's frequent failures in the domestic league, their chances of winning against Arsenal are decreasing and I think Arsenal with their consistency can bury Bayern Munich's hopes of going further. Of course, the Gunners are very confident with the instability of Bayern Munich so far and they will definitely try as hard as possible to get a win in the first leg.
I know it's not an easy job, especially since the first leg took place at Bayern Munich's home ground. But at least if Arsenal knew the weak points of Bayern Munich's defense then they could steal the aggregate lead first. If this can go well then it is not impossible that Arsenal will break the bad record in history when facing Bayern Munich. It might be a bit naive if we don't discuss this clearly, but Bayern Munich can't do much this season, especially in the Champions League.
While Arsenal are in their best shape and it is the opposite for Bayern Munich I'm really curious about what we will watch in these legs.

On the other hand I can't be confident about Arsenal fully after watching them against Porto previously. Arteta wants to win the Premier League title a lot finally. It is really not easy to keep a good balance between two big tournaments in such situations you know. Not every team are successful about that. If Arsenal don't improve their performance in the Champions League then it wouldn't be surprising at all to see them saying goodbye in this phase.
Yes, Arsenal will indeed focus on two competitions at once, but in my opinion they can still make the closest match a priority for them, whether the closest match is in the Champions League or in the Premier League. Arteta must also be able to prepare his team as best as possible for every match they will play.
Arsenal's meeting record when facing Bayern Mnuich is not very good, but that doesn't mean they can't improve that record by winning this match. They have a chance to beat Bayern Mnuich, as long as they can play consistently and don't make many mistakes.
Bayern Munich themselves will definitely focus on the Champions League, because in the Bundesliga they have been eliminated by Leverkusen. This will be a difficult match for both teams.