Let's see without kamui it would be totally different from the earlier shippuden fight.It would be high difficulty for the winner.
Nobody to babysitting here for Kakashi so he can save a lot of chakra, in addition of his current speed and chakra improvement.Also no knowledge mean probably kakuzu start in normal mode with doton skin, Kakashi will probably start with a raiton kage bunshin trap and doton underground and one shot him with raikiri.Then kakuzu will release his masks and Kakashi will have knowledge.
Kakashi can dodge every attacks ( he was able to dodge them and save team 10 in same times many times) , the raiton giant is easily dodgable for him, the major problem is his fusionned fire/wind combo which he can go underground since there is noone to babysitting here.Kakashi has capacity to outsmart the mask one by one sneaking attacks, Kakuzu's tentacles are cut like spaghetti with raikiri as we saw.Then once Kakashi destroyed the wind or fire mask it's GG.
Kakuzu can't spam attacks, perfect fight for kakashi .
Current Kakashi take this high difficulty just because of the number of masks.