Meh. Nico Robin had a bounty below every fodder pirate out there despite being the only one who could decipher the poneglyphs.
It should play a role but ultimately when you get into bounties this high these kinds of things don't do much to push it that much further.
And while it does play a role at the same time Kuzan's pirate career just started while Mihawk has been one his entire life so it cancels out anyway.
No it doesn't
Right off the bat someone who is at the highest rank of military has inner secretes and is a bigger threat to you than an average pirate of similar strength, using the word "average" very conservatively here.
And secondly Mihawk had his bounty frozen for a while and it was just the amount Mihawk got as a threat that WSS brings on individual level.
Surpassing your own captain's bounty and that captain being a Yonko with legit Yonko level bounty is even more impressive.
Kuzan is certainly not gonna have a higher bounty than Blackbeard.