I actually really think that Roger might have had an established hybrid fighting style.
During the clash with WB both channeled a non touching haki blast through their weapons instead of making physical contact.
And Kamusari also seems to be a channeled-through-sword-hakiblast instead of a haki enhanced airslash.
I think the trick might lay in the difference of power: CoC only amplifies stuff. Luffy never matched Kaido's base strength or Yamato's for that matter ( Oni strength ~ G3+), but he could keep up with either with ID CoA hakiblasts. That was seemingly indicated, when he fought Yamato and it was shown, when he started match Kaido's CoC club swings.
Luffy never tried to match up with Kaido with just CoC infused physical attacks.
This might mean that (ID) CoA hakiblasts (far) surpass human strength and therefore CoC infused CoA hakiblasts might even further surpass CoC infused human physical attacks, just as normal contact making physical swordslashes.
The latter might also be, where the black swords shine, cause Mihawk and Ryuma would break the opponents' weapon, thanks to a double layer of CoA hardening basically.
Gets further evident by:
Sabo matching Burgess power with ID CoA most likely. Hyo implied that Luffy could deflect O'lin if he masters advCoA. And Ray could block a giant elephant, that likely far surpasses his physical strength with a CoA haki blast.
So Roger:
Adv ID CoC hakiblasts = tremendous power + internal damage
Adv CoC infused sword swings = less power, but tremendous lethality