Looks like Luffy is not covered in CoA and CoC all the time in Nika mode, cause he still uses both explicitly for blocks and attacks. That's probably why the official translation went with "uses" instead of "covered", which just means that he uses internal destruction CoC attacks in combination with his super free fighting style.
His body just got so much stronger, similar to normal Zoan awakenings. That's basically CoA using base Nika vs CoA using awakend Lucci.
But Luffy still has that Hulk mode gimmick, the "making things rubbery"-gimmick, which he used offensively here, ggn Giant, partial gigantification and G4's compression mechanism.
I'm eager to see if Lucci can use seime kikan in awakened state aswell.
And I get the feeling that Kaido could only tap into awakening, when he was drunk, that's when stood true to his feelings, means his mind for the time being catched up with his body and the fruit and that's also why his haki increased.
Bro should have become some sort of Guardian Deity and he would have awakened his fruit no prob.
Might be, that you cannot awaken certain fruits, if your intentions aren't good natured or something like that.
And a guy like Lucci probably just has to like killing people in order to satisfy the most basic desire of his carnivorous DF and that's why this guy got it.