Hi and welcome to a document that will hopefully layout the way world generation functions in Cubic Chunks in 1.17+.
Cubic Chunks world generation is composed of cubes that are pushed through the numerous generation stages/chunk statuses. (Vanilla System but 3D)
ProtoCube (aka CubePrimer at the time of writing) is what's pushed through all stages of world generation to eventually upgrade to a BigCube.
ProtoCube is the CC equivalent of a ProtoChunk(extends ProtoChunk) BigCube is the CC equivalent of a LevelChunk(does not extend LevelChunk)