Dani Olmo's arrival is pretty good, Barca has strengthened the team. Olmo is a player who will be worth the big money paid. When he came to La Liga after the Bundesliga, it's admirable that he adapted instantly.
It's interesting that Barca won all three games same score, 2-1. In two of them they came from behind to turn the game around. I think all these oppontets were medium difficulty and it's good that they got through them without any point loss. Other contenders lost points and Barca are on top. They have more variety in attack this season and they can get Lewandowski more of the ball. The wings are working. I think they have everything to be hopeful for the title.
Only Barcelona have a perfect points so far (9 points from 3 matches), no one would be wrong to expect them to become La Liga champions this season, but that's too soon to say, we haven't even go to the first El Clasico of the season yet, so even though Barcelona are currently having a good run, we can't know how they will be after that.
About Barcelona's match against Rayo Vallecano, I thought Olmo played well, it's a shame he didn't play from the start, maybe if he played earlier we could have seen Barcelona's third and fourth goals.
We are still at the beginning of the league but Barcelona is continuing on their way with high morale. Playing without mistakes in 3 matches was an indication that Flick analyzed the team well. The main factor for Barcelona will be the El Classico matches. If they can get 6 points from Real in those matches, they will be champions this year, but if they lose 2, their chances of winning the league will be very low. They are lucky that Real Madrid got stuck with Mallorca in the first week of the league and lost 2 points.