Luffy all out is Ray lvl. So we can see what Ray can do against an emperor
How did you determine that? LMAO
One thing is for sure.... IN ANY SHONEN ANIME, when the student SURPASSES his master.... the author makes sure to highlights it
In other words, EVEN IF LUFFY beat Kaido SOLO
and Oda did not show/highlight that by some third party that "Luffy surpassed Rayleigh"
then that simply means Rayleigh is STILL stronger
That's an iron-clad rule in Shonen... remember it
Oda can highlight that moment by so many ways:
1- The Naruto/Jiraya style: a master defeated by someone, and Luffy defeats him
2- Luffy defeating an old rival for Rayleigh, who saw Rayleigh's prime strength and acknowledges that Luffy state surpasses rayleigh
3- Luffy meets Rayleigh again, and Rayleigh through his eyes, acknowledges that
4- Or both of them fight together and Rayleigh sees that he surpassed him
5- a Member from Roger crew fights alongside Luffy (such as Scopper Gabban) and he acknowledges it
And many other ways.... point is... when Luffy surpasses rayleigh, it will be 100% sure mentioned... cause Shonen always highlights the moment a student surpasses his teacher
It's why EVEN TO THIS DAY, even after defeating Katakuri... Luffy is remembering techniques from Rayleigh like the advanced 3rd stage Ryuu
We don't yet know if Rayleigh showed Luffy an advanced king's haki during training to demonstrate something.. or even more mysterious stuff