There are many old shounen anime with 2 boy and 1 girl, and with how close they're from being childhood firends, i think their dynamic wouldnt change that much if there are two girls and one boy instead.
Not to mention that shounen boys and girls are veing voiced by female VA. Sometimes i play silly game where i imagine that all three of them were just female, but two of them were boyish and have shorter hair.
And therefore, in my opinion, you can just act like how the girls just act like the sole male were just female with short hair and boyish acts.
You can also think of the male as the male friend in the group. Of course there are some private girls things that wouldn't be spoken in front of him, but otherwise he's just there.