Queen being an ancient zoan as well as a cyborg made him into a very dangerous fighter, he was also able to take attacks from Marco, Chopper, and Sanji and still keep fighting.
If you ignore power level, Queen is someone who has been shown to be extremely sadistic and we know that he has killed many people. Remember that the Beasts Pirates are known for their brutality, also Queen is a former MADS member so that is probably another reason why he has such a high bounty.
As for Jack, I don't have much to say in terms of power level. He was able to fight the Minks for five days on Zou, but on Wano he ended up being kind of underwhelming.
But just like Queen, Jack is also known for his brutality and he himself even said that he likes to destroy for fun.
The amount of places Jack has attacked and the people he killed is probably one of the reason why he has such a high bounty.
You don't need to have a mythical zoan or advanced haki to have over a billion bounty, King doesn't have a mythical zoan and he doesn't have advanced haki and Marco himself doesn't have advanced haki either and yet they both of them have a bounty over a billion as well.
Queen imo deserves to have a bounty over a billion, Jack on the other hand I guess you could make some arguments against him.