Luffy & Yamato vs Kaido. Snake Man Jet Culverin with Divine Swiftness White Serpent...

[doraemon]

Despite Yamato having far greater potential than the current commanders, I would still rate her as a strong pirate rookie level. To reach commander level, you need to have the life experience (fighting experience included) and maturity. Yamato is too young and has not travelled out of Wano, like Zoro. If advanced conqueror haki is all you need, zoro would not have beaten king.