Seriously, both matches are a difficult match for Barcelona and also, at the same time, a very important match for them, so they really need to win both of them. If they lose any, it will affect them, as you said, especially the La Liga, as they are already topping the league table. They won’t want to drop a point, and that is what makes it more important for them to win the match.
And also, Real Madrid needs to be at the top to get ready for the league title race, so Barcelona will not want to leave the position to Real Madrid, and at the same time, Barcelona will not want to lose against Bayern Munich because they will be playing at home, and both of these matches are very important for both opponents. Let’s see what will happen.
With that in mind, it's likely they'll have a higher priority to be consistent in the domestic league. Although results in the Champions League are also important but at least, there is still plenty of opportunity for them to at least finish in the top eight in the Champions League table. Thus, it is possible that Barcelona will try at least not to lose against Bayern Munich, because Barcelona also still has to make good preparations for the more important match in the El Clasico match later against Real Madrid. Because after all, in addition to Barcelona's less rest time compared to Real Madrid, that Barcelona will also play away. With factors like that, then although Barcelona still have to play well in the Champions League, but they may also rotate to still have good fitness for the El Clasico match later.
I agree league is more important, because we are talking about a team that is looking to win la liga more importantly than anything else and because of this I believe we are not going to end up with anything changing and we are going to see this result to be a very difficult one, we need to consider how this is going to be something that will not be all that complicated at all for Barcelona to give up on UCL before they give up on the league.
Not that they should, they should try to win both of them and I do not understand why they have to pick just one of the places and I bet that if they could end up with something that is going to look very differently. What we need to consider right now is a team with 70+ million salary every year should be able to play for both games.
I believe Bayern will end up getting a win, so Barcelona can't really have both losses in these games, they have to figure out a way to get win at least in one of them if not both. If they get both wins then they are going to have a huge morale and they are going to end up with a great period after that because they are going to have high morale and they are going to face easier games so they can go on a winning streak.