You didnt tell whether both teams have info on the other therefore id assume both dont have acknowledge at all.
If thats the case, akatsuki takes this with mid and possibly hard difficulty.
Kakashi cannot fight on par with kakuzu. His best chance is to use kamui and he said this in the manga. Unless he can teleport a whole body which he only tobi has demonstrated this feat, he would merely wound kakuzu. Thats off course if one of his hearts does not intervene.
In the manga when ever kisame has faced gai he has always been at the disadvantage and yet gai's wins havent been convincing. We saw how a 30% chkra kisame clone, forced gai to use his nin chuck, but also open 6 gates. Just to defeat a kisame who wasnt even at half his strength
Simialr in the second scenario, kisame was greatly weakened from hiding in samahada all the time. Not only was he weakened in terms of his usual chakra supply, he didnt have samahada with him. Whilst its true gai doesnt use chakra, if kisame had samahada if it came in contact with gai, it would absorb his chakra, not to forget with samahada kisame can fuse, which is like his very own sage mode. Increase in speed, durability and strength. We saw that gai's strongest attacks didnt break a weakened kisame.
All in all, its clear as day that the akatsuki are the stronger of the two, but also due to their encounters in the manga, without any plot, kisame and kakuzu would beat them