The combination of Arda and Endrick is indeed interesting but in the second leg I think Madrid needs to give a definite step in this match because it will determine whether to enter the next round by entering Mbappe the potential for victory is much greater, I think Ancelotti will take Mbappe for the second leg because if you look at the current aggregate it is too thin to take risks with the same strategy.
Victory in the second leg is very important so if you apply the same players I think it is too risky, but it can be an option only for the first half and the second half using its real strength, it should be remembered that Real Soicedad is very dangerous seeing the match in leg 1.
Real Madrid has good capital in the first leg even though the aggregate is still not so safe, but if you look at the quality of Real Madrid when facing a team that is much weaker than them then I am sure Ancelloti will use the same formation. The second leg will not be that difficult as long as Real Madrid can play as usual and maybe the difference later will be that there will be several players that Ancelloti will try to rotate.
But I am sure Real Madrid will win the match in the second leg because if you look at the potential that exists, Real Madrid is much more favored to win the match even though Real Sociedad put up quite a fight in the first leg.