On paper Real Madrid are far superior to Salzburg and Brest, but anything can happen as long as the match is still in progress. Although the chances for both clubs are very slim, it could be very decisive and could punish Real Madrid. What just happened at Anfield when Man United held Liverpool to a draw could happen to Real Madrid.
This match is very important for Real Madrid to determine their fate in the UCL, they must take advantage of every opportunity and prevent the slightest mistake so as not to lose points at a crucial time.
Honestly I will not underestimate RB Salzburg and Brest, moreover Madrid is still a bit unstable when playing against teams below them. However, because this is the Champions League, at least Ancelotti and his troops understand the atmosphere on the field much better. Talking about the Champions League, the most important thing is the mentality to play until the end, therefore RB Salzburg and Brest must be able to match the mentality of Real Madrid game. That is the only key that other clubs need to prepare when playing against Madrid.
I also think so, overall Real Madrid's performance this season is very inconsistent and also the matches in UCL cannot be underestimated especially overall the strength of RB Salzburg and Brest is not that bad this season so it is also possible for RB Salzburg and Brest to make a surprise when playing against Real Madrid later.
I think everything is possible in the remaining 2 UCL matches before the playoffs later and I think Real Madrid cannot be favored excessively.
Maybe Real Madrid has performed poorly in some Champions League matches, but when a match was very important for them to stay in the Champions League, Real Madrid performed well and secured victory. If we can't consider Real Madrid as the favorite team for the Champions League then we will consider any other team as the favorite for the Champions League. I have also seen many seasons where Real Madrid finished second or third in the points table in La Liga but they performed well in the Champions League and in many seasons they won the Champions League title.
If there is ever a proposal in front of Real Madrid that they have to prepare for any tournament in the Champions League or La Liga, then they will probably prepare for the Champions League without a second thought. I still have full faith in Real Madrid and I believe Real Madrid will do well this season as well.