Among these three strong teams, Barcelona does get a fairly weak opponent compared to its two rivals, but that doesn't mean it will be easy for them to beat Real Sociedad, I have seen how they played against Madrid yesterday, it was a good game from them. Hansi Flick still has to prepare his best squad so that victory and the main place in the standings are still theirs.
I don't know how you guys have concluded that Sociedad is relatively easier than Betis. Don't forget that Sociedad have beaten Barcelona once this season already and that was the worst performance that Barcelona have had this season.
I think the advantage Barcelona has is the fact that both Madrd teams face each other in the Champions League so I believe they might not use a very strong squad and that gives their opponents a chance, especially Athletic Bilbao.
Atletico Madrid has the toughest opponent this weekend and I don't think they will get all 3 points. Madrid on the other hand knows how to win games like this so I also expect them to win.
For my prediction, I'll say a win for both Barcelona and Madrid and a draw for Atleti.