I know Brave could be anyone, but weight logic doesn't seem to apply in Smash. Aren't you forgetting that Mewtwo is literally one of the lightest characters in the game but canonically 269 pounds? Charizard is only 200 and even heavier than Mewtwo in Smash. I mean, Geno's easy to pick up when he's a doll, but we have no idea how much he weighs in his grown form. In fact, NOBODY even has a specific weight for Geno, not even Square themselves because they hardly even bother to give him or Mallow an official weight.
Correct me if I'm wrong, but isn't Geno being light just a fan-made thing? I'm pretty sure Geno could be light or heavy, however, it made me come to realize that the amount of wood, plus the ammunition inside his arms, plus turning into a cannon could weigh a lot. Remember that Geno keeps tons of ammunition inside of him and uses guns for his arms, which probably makes his weight/mass heavy. If anything, Mallow seems more like a light character due to him being small and a cloud, while Geno is more of an average (Mario weight) weight character due to the amount of wood and stored ammunition inside of his body.