If Kuzan didn’t have a 3B bounty, I’m pretty sure Oda would have just revealed it with the Admirals and Garp’s.
Assuming Kuzan also had 3B before Garp's defeat, then his bounty should be higher now bc obviously he participated in bringing down Garp, infact he contributed the most.
And if he does participate in BBP vs RHP, and beat someone ( let's say Hinokizu / Burn Scar Man ) then his bounty will be even higher
But his strength will stay the same. In a lot of cases bounty =/= strength