Nothing they have done should put their bounties above Luffy’s that’s for sure
There's a lot that goes into bounties though and each case is different. Feats-wise, Luffy "should" have the highest bounty in the series because he defeated the person with the highest active bounty.
But there are a lot of ways to explain why his bounty isn't there yet:
1) The WG purposely kept his bounty low in order to keep hiding the return of Nika
2) They accredited the downfall of Big Mom + Kaido to Luffy, Law and Kid collectively (without differentiating) and split the bounties 3 ways.
3) It simply takes years of being in the game to build up your bounty into such high ranges.
When Brannew revealed the Yonko bounties, it was explicitly mentioned that Shanks is the youngest and has only been a Yonko for 6 years. A lot of people took that as an explanation for why his bounty was the lowest of the original 4.
Also, Blackbeard did so fucking much across the entirety of the series, yet he still only has/had a bounty of 2.2B as a "rookie" Yonko.
Mihawk & Croc have been in the game for decades. Even if they have no singular "feat" that matches up to what Luffy just did, their experience is something the WG likely values considerably.