EoS Zoro is going to be the King in physical contact combat. I don't even know if Ryuma is the ceiling there.
Oda's baseline for that seems to be a) a weapon of choice + a refined fighting style b) CoC coating and c) atleast basic FS - Gaban, Kaido, Mihawk..
Add a black blade and that already might have been Ryuma's whole stack. It's powerful and makes him a solid top tier, but I don't see why Ryuma should be a high ceiling.
Zoro has 3 extra perks on top of that baseline stack already: KoH, Santoryu advantages, Asura..
After the Mihawk fight his baseline ability stack will likely include Ryuma's whole repertoire, hence he will likely end up being Santoryu Ryuma at base with all those fancy extra gimmicks.
It's likely that Mihawk is superior to Ryuma btw. With Asura, Enma, Cerberus, Gryphon in the game, Mihawk will have his own special ability aswell I bet, which might make him a Ryuma type of guy + a unique special ability.