In this case, a Concept-Driven game is a game who's focus in on a centralized concept, but doesn't really focus on any specific characters or setting. Think Nintendogs, 1-2 Switch, or Wii Fit. Character-Driven games are games that focus on core gameplay idea, represented by uniquely designed and distinct characters created to fit the central theme and mechanic of the game, IE Splatoon's Inklings being squids because of the Ink mechanic, and the ARMS characters having extendable arms because of the 3rd person stretchy arm mechanic.
Ring Fit, in this context, would fall much closer to the character-driven side than the concept driven side, since its main focus is on the adventures of a Fitness Hero with flaming hair, and sentient, talking Pilates Ring that represents the controller, and a fantasy world and characters themed after the fitness and exercise mechanics of the game.
The way you're defining it, then this is clearly in the second category. The game definitely has characters. I'm just not sure why the distinction is worthwhile.
On a semi-related note, I think that a Wii Sports type game with a structure similar to this might be fun. Maybe get the golf story guys to work on it.