How good is he? who do you think is the best grappler that he can out grappler in UFC history? both he and his opponent is in their prime If you were to rank him among the best MMA fighters would he be in the top 100 or no?
No doubt He is the champion of the UFC. If you compared to him the other best grapplers in the UFC then there are many more fighters who are the best.
The fact is This content is protected ranked number 5 on the one Lightweight rankings of October 2022. He is the champion of All Japan Jiu-Jitsu, Japan Open Jiu-Jitsu, Budo Open Championship, and an ADCC Japan which claimed that he is one of the best grapplers and a professional MMA World Champion.
Grappling wise, honestly, he would lose to even Conor Mcgregor(in an mma fight). Most modern 155lb wreck him. You'd have to go back to 2010s to find a viable grappler. The sport has surpassed him far. Eddie Alvarez smashed him in r1. I think he gets wrecked even by a striker/generalist like Dan Hooker, Poirier, or Gaethje.