King definitely hasn't proved that he's stronger than Katakuri but it's not impossible. He's most likely stronger than Queen based off portrayal, their interactions and roles in the crew. How large is the gap? It's unclear. I wouldn't be surprised if all 3 were kind of close in power but it's most likely that Katakuri and King are close and Queen's a bit behind. I doubt King and Katakuri have even fought before but considering that they focus on different aspects of combat, they might be close in strength overall.