Law and Kid bounties are equal to Luffy because the world government and Marines believe those three work together to defeat Kaido and Big Mom in a group battle.
The truth is Law and Kid weren't strong enough to do anything significant to Kaido and need a bombs to beat Big Mom. King could have done the same thing with bombs. Big Mom and her entire crew couldn't stop him by himself. They're in the same categories Buggy. Lucky pirates riding somebody else's hype.
Let's see those do you do something significant by themselves before we even attempt to compare them to Zoro.