Yes, we will see Real Madrid will give a surprise in UCL when facing Arsenal, Real Madrid will likely win by defeating Arsenal. I think Real Madrid players do not need to doubt that they have many great players and also have Ancelotti, a coach who has a good career in UCL. The team's performance in healthy condition, there is no doubt that Real Madrid will be superior. Discussing Arteta, he is a good coach, and has enough creativity in organizing and making new designs for a team that is almost equal to Ancelotti, I also see both of them as the best managers and both have different tactics.
In order for Arteta to be perceived as a good coach, he needs a big win, beating Real in the Champions League would be a great step for this, but everyone has big doubts about this. Real is stronger in players and Ancelotti has much more experience in the Champions League, which of course plays a huge role at the playoff stage, where even one mistake can decide the outcome. It seems to me that Arteta will have another season without trophies.