no hes not, and gai fought kisame without samehada which is a big deal
i dont understand why people keep saying this.
How would samahada help to fight gai.
If kisame couldnt absorb gais moves samahada cant either. And if samahdada cant help by absorbing chakra is just a blunt sword.
And gai didnt even have his nucchucks either. Gai clearly had good match up against how kisame fights. Kisame steals chakra to blunt his enemies techniques but cant do that against gai. Main reason why hes was good to deal with hosts like bee.
Its very logical dude
As for kahashi, given the massive speed and strength differnece, the only chance kahashi would have is to use his MS timespace jutsu which means this chakra will be cut short and if hes is unsessful in catching him.
So I think Gai would come out on top, all depends if he could catch gai in MS jutsu, at this point it looks unlikey gai is way to fast.