La Liga has gone through three matches since the season started, the three favorite teams who usually always compete for the title have achieved different results, Real Madrid managed to get full points after getting three consecutive wins, Barcelona was only able to get 2 wins and 1 draw, while Atletico Madrid was only able to collect 2 points from 2 draws and 1 loss. However, Real Madrid is not guaranteed to win the trophy because their success at the end of the season depends on their performance while the competition is still running.
In later months of season, players will become more tired, even exhausted and this increases risks of getting injuries, absence and underperformances for their clubs. Last months of season will decide the winner between Barcelona and Real Madrid and which club will be a champion in La Liga this season. Now the season is still in very early weeks, and many things can be changed in many months ahead. Any advantage now can not guarantee anything about the title winner at the season ending.
At this stage of the league, that's almost irrelevant. Last year, Madrid also started ahead of Barcelona, and it wasn't until well into the second half of the league that Barcelona managed to take the lead. So I think that until at least the 20th match or so, we won't be able to speculate with any certainty about how things will turn out.
Real Madrid and Barcelona are strong and experienced in title race so their race with each other will have many twists. With their ability to make domination in La Liga, they will not lose many points to other clubs in the league and their point difference with each other will likely not be too big. It is an opportunity for any twist to appear after one or two match days and they can flip their ranks with each other several times in this season.
A club that manages to flip rank and take over a first position, then hold it in last several match days will become the champion. This important twist can appear after UEFA Champions League comes to knock out phases, especially quarter final or semi final.