My thoughts on this are that in this Covid football season you're seeing more games, in all leagues, where teams are obviously playing without fans but also regular games with squads often missing more players than in a usual season. They definitely have more of a pre-season feel to them not only because of the lack of atmosphere but the change in pace of a game that crowds can bring, so the games end up more like "trading blows", going back to more typical Premier League football where teams go at each other with less tactical pressure, less crowd pressure, it suits some teams better than others.
These things suit United because they have an attacking coach with a squad who are clearly better in the attacking areas than they are in central midfield and defence. They have fast and technical attacking players (Pogba, Bruno Fernandes, Martial, Rashford, Cavani, Greenwood, also added Amad Diallo now) who will exploit these kind of conditions. I think the lack of pressure from the OT crowd helps them. United fans are not known for getting on players' backs at OT but inevitably at a club who was used to winning every year who then had a succession of failed seasons post-SAF the players feel that pressure, when things are not going right and they hear a few moans from the crowd or the crowd goes quiet as the pressure builds it is different from these games played under exhibition conditions.
By contrast I don't think these conditions help a team like Juventus. We have experienced players used to winning big games in pressure situations, the loss of our home crowd and its closeness to the pitch is a big negative, just as it is for many other teams. We'd have teams beaten before the whistle in some games, but in these conditions it's far more of an equaliser having this home advantage removed.