That's not really the point. Doffy was excited at the thought of having to fight Whitebeard's force period.
Doffy was weary of Kaido because he knows Kaido is ruthless and unreasonable. Kuzan, however, is not.
Another testament to Doffy's emotions not being a good indicator is that he went back and forth being scowling in rage at Law and Luffy and smiling the entire fight. I suppose the moments he was frowning he considered them bigger threats than Kuzan then changed his mind when smiling, then back when frowning again? Because that's how his emotions work, right?
There's no reason to speculate Doffy would be excited to fight WB in a 1v1, which is the only viable comparison you can make with the Kaido situation.
Not sure what the rest is supposed to imply. Doffy smiles most of the time as it's a part of the 'crazy/joker-like' persona Oda attempts to convey. One of the very few situations that he did not smile in was when Kaido's name was brought up.. I even doubt Doffy would get manhandled against Kuzan, he's a rather underrated character because people think 4th Gear Luffy 'destroyed' him even though he beats 4th Gear Luffy post-huge organ damage. He's already been portrayed as Jozu's superior, who has quite a bit of portrayal going for him. And then there's also the fact that Kuzan called Doffy an exceptional fighter, and wanted to relay this information to Akainu, almost to say that they should be weary of his strength. I'm not saying he can beat Kuzan, or any admiral, but I do believe it would be a high diff fight. Kaido
wiping the floor with Doffy implies a low-mid diff fight, and I highly doubt that given this, Kaido would consider Doffy an 'exceptional fighter'.
Then there's the fact that Kaido is the strongest creature/human/pirate alive. So it's rather obvious that he's superior to all the Yonko and Admirals. We also have BB, who by now should have decent control over the Gura Gura, and already has exceptional control over his Yami DF. BB's also one of the greatest tanks in OP verse after taking that hit from WB, those shockwaves from Sengoku and those spears from Ace. A few more years of progression through the time-skip and he'd have by far more hype then what any of the other admirals have. I'm really not seeing how anyone can suggest the admirals are comparable to the Yonko. I mean the Yonko's first mates/first commanders have pretty much been portrayed as admiral level lmfao. Marco vs 3 admirals portrayal, Rayleigh vs Kizaru despite his age, Ben Beckman's power being 'feared' by Kizaru while he's behind him These are the only confirmed Yonko first mates/first commanders, but it's safe to assume Big Mom's and BB's aren't much weaker if they've been fighting on a comparable level in the past (apart from Gol D Roger, but then again Rayleigh would be stronger then an admiral in his prime). Saying the Yonko's themselves are admiral level when their first mates have shown to be admiral level seems fallacious to me.