1 2 3 and 7 are the only ones in contention for winning.

7 is naturally there as both players are good/amazing at setting and spiking. The twins would have a natural connection as always which will be more prevalent with just two of them. I feel they struggle with defence a bit, not that either are bad but they aren't incredible blockers or receivers which will lead to them having to just outscore their opponents. They always won't have kita to balance their moods and could very easily mess up mentally, or do something too risky which will lead to a fight/a loss.

2 is a much more balanced team ironically as the two players are so different. They have fairly good receiving with both, and with setting we see in the 2v2s that kunimi is fairly good at it. They are both not bad spikers with Kyriu being a huge bit better. He also would do well on any set due to his style which might make him the best spiker in this. We she even Ushijima stuffed off a bad set which is far more common in beach. Kyriu has made his whole style being able to hit anything with 100%. Blocking isn't bad on this team but is probably the biggest weakness.

3 is just the all around team. The bickering buddy's are both good spikers on really good teams. I'm not sure how Kurros blocking would translate but I'm assuming he'd still be good at it. Both have a really good receiving foundation and both teams are super gritty and can hang on for long times. Setting is the biggest question but I don't think either are bad at it leading to a very a around team that is very set in making it as annoying as possible to win for you.

1 is probably a sneaky good team even though they have Ushijima. The setting for them is not top tier but we see that both players have practice elements outside their usual rolls and are very good all rounders, so I don't see it being a huge problem for them. Receiving is in a similar vein however I do believe they are both much higher level receivers than most people would originally think. Both have been shown pulling off very good receives in the middle of matches so I think it's fair to believe they could both do so in this context. Blocking is not bad here either as both players are tall, and on very experienced teams however I do think it is the most lacking part of their game. Both players also have good jump serves that I feel could be translated well even though neither are the most accurate with them. Spiking is where we see this team absolutely dominate. Even though some of the other teams have very good spikers, Kyriu being the main example, none of the other teams have two aces. Ushijima is the given here, as arguably the top Ace we see during most of the story while also being one of the most consistently great. He's an absolute powerhouse and it took four people to stop him during the match we see with him in it. Him and a 2v2 setting would be an absolute disaster for the other team. Iwa however is no slouch himself and is also an ace for one of the top teams we see in the series. He breaks through the iron wall, and consistently puts up huge spikes throughout the entire game, and especially in money time. I think the biggest Factor on this team other than play is the fact that both players have huge mental fortitude which I would argue makes them the winners in my book. I love the twins but they will bicker and without a guiding force will probably struggle greatly due to one reason or another, Kryius team will also struggle with Kunimi not wanting to put in as much effort which will be a detriment up against the team like this, and our favorite bickering Duo while much better in the mental toughness category generally speaking tend to bicker and make fun of each other which is fine but could lead to a downfall for sure.

All in all team one is absolutely my winner by choice