You're jumping to conclusions, WhosWho wanted to challenge a Calamity, pure speculation but what if WhosWho want to fight King and has history with him. What's to say that Sanji can solo Queen? Those might not even be the final matchups if the raid fails. WhosWho could even switch sides. You're taking things too much at face value.
Jinbei offered a deal to Big Mom, to promise to not harm anyone but him and Big Mom accepted the deal. So there's nothing there, the one she's angered at is Strawhat that's why she's in Wano.
His mission is to attain true freedom for the Fishman race and he thinks he can achieve that with Luffy because he believes he can become the Pirate King. The Pirate King is the freest person in the world, plus Luffy will eventually challenge the World Government. Jinbei is the ambassador of his people to bridge the gap between Fishman and Human. Only Jinbei can accomplish that, that's why he made Luffy be the hero of Fishman Island to break the cycle of fear, so on the opposite it has to be a Fishman who's willing to take on the fear of humans by reconstructing the image of the Fishmen in the world and it's starting with the notorious criminal fishmen pirates on the seas such as Jack, building a good name for himself and his people. He's come from a long way, carrying a lot on his shoulders, the will of Fisher Tiger and Otohime. It will be a hard path for him to face the discrimination of the world. People fear what they don't know..
We seen them bicker many times, but they never fought each other. Being seen side by side is a moot point to claim that they are evenly powerful.