Ryuma was the strongest samurai. I don't see Oden as a balanced blade type like Mihawk. He's a mighty blade type like Zoro and Ryuma. Mihawk has the perfect balance of the two.
I'm talking about Recent Era (Roger Era + Shanks Era + Current Events), not Strongest of All Times
Zoro combines both Strong Blade & Gentle Blade
Any Technique where Zoro tries to Blitz his Opponent or Hit them before They can is a Gentle Blade Technique
Any Technique where He tries to Overwhelm his Opponent or Flex his Power/Strength is a Strong Blade Technique
Mihawk is WSS, His Swordsmanship is Superior than Vikings, Samurai & Knights
The Idea is that Oda used Oden to Hype Samurai Potential, and i believe Shanks is gonna be the Oden of Knights and Giant Vikings gonna have such Character as well, but Mihawk is Stronger than All Three
Oden is indeed classified as Strong Blade Swordsman, so were Zoro & Zombie Ryuma by Brook
But that doesn't mean They do not use Gentle Blade, this Categorization is for which Stat are They better at
So Zoro, Oden & Ryuma Combine both Strong & Gentle Blade, it's just that their Strength is better than their Speed
Oni Giri is Prime Example, it relies on both Strength & Speed/Precision, but it relies more on Strength, cuz when Zoro wants to use his Max Speed, He instead switches to One-Sword Style (Lion's Song relies almost entirely on Zoro's Speed)
Elbaf's Swordsmanship however completely relies on Strength, Big Mom & Dorry do not rely on their Speed at all, They fully flex their Strength in their Attacks, and as for Knights, i believe They Fight like Hakuba, meaning They completely rely on Blitzing their Opponents
Think of it this way:
Vikings = Pure Strong Blade (Doesn't mean They can't be Fast)
Knights = Pure Gentle Blade (Doesn't mean They can't be Strong)
Samurai = Imperfect Combination of The Two (60-40%)
Mihawk = Perfect Blade
I called Oden's Swordsmanship as Balanced which wasn't Accurate, i just meant He combines Both (Imperfectly)
As for Shanks, i believe this is the reason He didn't lose any of his Power when He lost an Arm, cuz He can use Pure Gentle Blade Attacks
Meaning He completely Blitz his Opponents before They could even React, and He already did it with Kid and also in Non-Canon Movie Red against Kizaru