Indeed Real Madrid opponent is a slightly easier rather than opponent Atletico Madrid, so yes there is a chance for Real Madrid to get points against Atletico Madrid. Because yeah there is a possibility Diego Simeone squad is tired, but in the last few matches Atletico Madrid have a good performance. Anyhow, Diego squad looks solid I doubt Real Madrid can win, but be expected Ancelotti can find a suitable tactic in that match at least to surive for draw result.
Actually, in La Liga, Rea Sociedad is also not a small club and has sometimes given good surprises. It's just a matter of how Real Madrid can optimize its performance again or not. But usually, Real Madrid will be superior to this club. If you look at Head 2 Head, Real Madrid clearly won more. Meanwhile, on the other hand, Atletico vs Valencia, I believe Atletico Madrid should not experience high obstacles. Valencia didn't start the season very well. They are still inconsistent and sometimes cannot optimize their chances. Here, Atletico Madrid might still be able to gain more advantages than Valencia.
Meanwhile at UC, you could say that Lazio is tougher than Berlin. However, no one can guarantee that because sometimes German clubs can also provide quite strong surprises in the Champions League. But of course, which club can handle more, the results will be more optimal.