When he uses their chakra + KKG ===> It'll lead to another form of FRS (e.g : Lava release rasenshuriken)No. He uses their chakra to add to his RS/Rasengan. Each time when he used their traits or KKG he used their chakra not only KKG.
When he uses their chakra only ====> It'll lead to a bigger , stronger FRS (e.g : rasengan improved by kurama's chakra)