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 cannot assume that Barcelona will win the league title this season. To be honest, if Barcelona wins the league this season, I'll be surprised since I never expected them to win the league with the academy players that fill up their squad, I was only seeing new faces against Rayo Vallecano, and the young players aren't very good at defense. However, Olmo had an outstanding performance in his debut for Barcelona, once he was substituted, the entire game changed because Rayo Vallecano dominated the first half of the game. Olmo had an impact on their performance in the second half and scored his first goal for the team, after his outstanding performance on his debut, I believe he will be selected among the team's starting players.
Hansi Flick's team look quite decent. Even in times they struggle they find their way out of it. This is important on the road to the La Liga title. Apart from that, I want to see how they play in big games like against Real Madrid and Atletico Madrid.
Did you think Barcelona could win the game without Olmo? Barcelona's performance was so poor in the first half that someone asked me whether they were the team wearing the white jersey

because the pressure was too much for them in the first half, so, unlike other big teams in the league, Real Madrid can win games without Bellingham, Vinicius, and Rodrygo because they have solid players to cover their positions. I doubt that Barcelona will compete with any of the big teams this season.