1-3 didn't have a concept
CAP 4, Fidgit, was pure utility. Moves like Trick Room, Tailwind, Gravity, entry hazards etc.
CAP 5, Stratagem, was break the mold. Essentially, the concept was to go against the stereotypes of a given type. In this case, it is Rock.
CAP 6, Arghonaut, was a decentralizer. it was built do decentralize the top 10 threats in CAP at the time.
CAP 7, Kitsunoh, was designed as the ultimate scout. It was built to gather information easily on the opponent's team.
CAP 8 was Cyclohm, and it's concept was neglected ability. Its ability was an ability that was neglected in the metagame because of various reasons. Shield Dust, in this case, was an underused ability in the current metagame, for example.
And I hope you've been following CAP 9 enough to know our concept!