Power scaling in op is mostly based on portrayal, cracker is a third yonko commander and based on big mom and kaido's crews portrayal he is probably around Jack's level of strength
Hell, Cracker was introduced as an opponent for Luffy to defeat within 5 chapters with a fight that took less time on page than Jinbei vs Who's Who, while Jack came as a formidable "wall" that the armies of Zou could not break down river 5 days.
And secondly "Third Yonko Commander" does not exist. It is pure fanmade nonsense.