Okay, let's think about it this way, the numbers were there with Kaido since 20 years ago, at that time, Kaido probably didn't had this complex ranking system since the crew was smaller. But with the addition of the headliners, the original members (numbers and calamities) were promoted to All-Stars; and don't forget that the numbers in card games are directly below the face cards. So I think that at the very least the F6 and numbers are equal in strength and match BM's older children.
If we want to compare their strengths;
BM:
-Sweet commanders
-Perospero and Snack
-Compote
-Daifuku and Oven
-Amande, Mont d' or, Tamago, Streusen, Galette and Opera
-Other children like Raisin, Yuen, Opera's siblings, the decuplets, Cracker's twin sister, Bavarios etc....
All of those are considered to be Yonko commanders btw, some of them are stronger than the others
Now for Kaido's commanders:
-Calamities
-Numbers and F6(they're at the same lvl but command wise the numbers are higher)
-Headliners