Well I really just see it as a case of them being emotional and being teenagers.
I honestly think it gives them complexity, where I live there's tons of people like this: they genuinely seem to be stupid or not present at times or extremely emotional but they really are smart when it comes down to the right moments.
Eg. For the last guy you mentioned, I see it that he's smart but because of what he's gone through And the emotions that he's kept pent up since that time- they all came crashing down on him and he reverted back to an emotional and pathetic state. The pathetic state I'd say is what we've seen in the flashback when the team members expresses their laissez-faire approach to football.
I mean I didn't see him as a character that was made as extremely smart- just someone who maybe is able to be rational and use their brain to think out a plan and get the help of others to carry it out. it's like when you watch a cartoon and there's this map reading character that is usually level-headed and can make a plan that would work for everybody but as soon as bombs start to blow up he becomes flustered unemotional on you could see mentally unstable as well.
If that makes sense? But i understand what you mean
Obviously though some of the moments are really just meant for comedy relief and cause inconsistencies in characters.