Kuma beats Boa. I think he won't be affected by her mero mero ability which is a lot of Hancock threat. Hancock also has all types of haki but I don't think her CoA would be enough to beat Kumas paw paw fruit and I don't think her conquerors haki will be a factor against a shichibukai level opponent.
I'm not sure if Mingo would be snared by Mero Mero...I don't think that guys heart is capable of loving anyone that isn't himself. He's shown incredible endurance and ability to take powerful blows so I don't think Boa could knock him out. Mingo on the other hand has stupid destructive power and could definitely kill Hancock. Much like the Kuma fight, Hancock depends on her ability stunning Mingo to win. I don't think it would work on Mingo which is why I think she will be beaten here too mid/low diff.
Kuma is hella strong. He can seemingly block any attack with his paws, he can move at incredible speed and he can create that air pressure bomb and pain bombs and also if he doesn't feel like foghting you he can litterally send you packing to another island. Even with Luffy's progress I don't know how he can defeat that. Maybe now that Kuma is an android without his original brain his fighting power won't be the same (just like how the pacifistas were weaker than kuma). In that case Luffy would have a chance.