Real Madrid and Barcelon will meet two opponents with nearly same quality. Rayo with 35 points, Osasuna with 31 points, and those clubs are fighting for high positions behind top four to be eligible as La Liga representatives in Europa League and Conference League next season. They are nearly same opponents for Real Madrid and Barcelona but Real Madrid will have disadvantage by playing a homeaway match and Barcelona will have advantage by being the host.
Maybe for Bilbao and Villarreal, I strongly doubt for those three leading teams (Realmadrid, Athletico Madrid, Barcelona], the point difference will take up to 5~6games points while for Bilbao and Villarreal, maybe just 2~3 games poimt which is somehow still a big barrier imo .. besides, that's Rayo, Osasuna will need almost a game + points for each.
Henceforth, you see that top 3 spot let's just leave it for the three gangs for now unless Bilbao will be joining soon.