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.
I bring this up because Splatoon has been recognized by both fans and Nintendo themselves, as the first new character-driven property created by the now-defunct EAD division since Pikmin in 2001. Since then, EAD began focusing more on concept-driven titles aimed at non-gamers such as Nintendogs, Wii Series, and Big Brain Academy, which while new IPs, weren't character-centric the way games like Splatoon were. Meanwhile, other teams within Nintendo, specifically teams within the SPD division, carried the mantle in developing original characters and worlds, though they never got the fame or recognition as EAD.
Since the Nintendo Switch, Nintendo has tried to make a full clean break from the Wii/DS approach to developing original games, and doubling down on its core focus as a Character-based entertainment company, rather than just a game publisher. Ring Fit Adventure is a continuation of the Splatoon/ARMS/Sushi Striker trend in developing new IPs in-house, rather than the old Mii/concept-centric approach of the Wii and DS.