I am being asked the question of "to be patient or to rush" and both answers are wrong.

I know this is just a demo but I still feel like I should be paying for this, this is fantastic

Very enjoyable, satisfying core gameplay and nice aesthetics. Good stuff basically. Here's my personal tier list, interspersed with some stuff I'd change.
#1: Pico. Pico's main strength is his projectile being unbelievably safe for how much reward it has. Aside from that, his forward air is both an easy combo starter and extender. Generally Pico can just rack up a lot of damage with little risk, which is, well, exactly what you want.
#2: Nene. Nene doesn't have anything quite as safe as Pico, but she does have the most consistent combo game out of the three once she does hit. She also has the highest speed, which in a game with no blocking is crucial for getting out of disadvantage.
#3: Darnell. Unfortunately, I think Darnell's moveset fundamentally doesn't work. He's slow, with slow moves, but when he does hit he hits hard. That's a fine archetype, but it just doesn't work in a game where combos are this pivotal. His speed also hinders him from finding openings to use his projectile, which is disappointing, as it's the longest range one in the game. Generally Darnell seems to be built around keeping a distance from his opponent, but that's just not something he can do. A block would likely help here.