I don't think Barcelona will win any of this trophies, they might be sitting on top of the table for the time but I have a feeling they will drop below that position when the league resumes. The Europa league also have many other teams who are looking more dangerous and ambitious than this Barcelona team so I doubt they will be able to win the Europa league or even the La Liga title this season.
Maybe your guess is right. But Barcelona's performance is quite commendable now. They are performing well and winning. At the same time, they are trying to solve the internal problems of the party. The bonding between the players is still not good enough. If Xavi is able to solve the small problems within the team, Barcelona's performance will be stable after the World Cup and they will be playing for the title. Xavi now has the responsibility to strengthen the Barcelona team. Barcelona will win the title if Xavi does his job properly.
When referring to the head-to-head record of the two teams, Barcelona is still ahead of Man United, but I don't think Barcelona will be able to win this match easily because Man United will definitely fight fiercely. Even though their performance has not been consistent, but Man United often looks good when facing big teams. Besides that, Barcelona also seems to prioritize La Liga. It was so obvious when they had to be eliminated from the Champions League. So I think, Man United also has the same opportunities as Barcelona to win this game.
Manchester United are yet to find their best form. Although they have won the last few matches, but Manchester United team has to fight hard to win in every match. Manchester United has dropped points this season even against weaker teams. And it is very difficult to win against Barcelona with an unstable team. But Manchester United also have a lot of talented players in their squad. They will certainly want to stop Barcelona. Barcelona won't lose against Manchester United unless they are unlucky.