In Kurama Mode, Naruto is fusing both his chakra supply and Kurama's chakra supply together, which means that the volume of chakra he controls in that form is superior to any other form he possessed until he achieved his newer forms. In that form, he gains Kurama's chakra control, which allows for easier use of jutsu, and his speed sky rockets to the point of he moves faster than the speed of sound. It is worth noting that Naruto's own chakra supply is comparable to Kurama's, since whilst in Sage Mode, his chakra was strong enough he could battle Kurama on a level playing field. Hence why his Kurama Mode is so much stronger than his Nine-Tails' Chakra Mode, and the senjutsu-enhanced Kurama Mode even more so.