They are all mods of the Hackless version, and tend to change the overall gameplay. Project M, the most popular one, changes it's mechanics to be more closer to Melee. Brawl Plus as far as I know is a mod that balances Brawl, and removes tripping. Brawl Minus essentially balances the characters by making them all broken. You'd have to play them yourself if you wanna get into further detail.
So, from my understanding of what you said, those are just codes that are different for each mode, so models and textures and such would work for any of those modes, right?
