definitely sage mode: increased chakra, speed, strength, reflexes...just like going super saiyan. which reminds me, why is nine-tails the only bijuu that can go kcm or bm, what about the other perfect jinchuriki's like bee and yagura?
Well not really. Even though Naruto has to draw his power from nature chakra, the act of actually performing the absorption and the applied use of it (Complete Futon Rasen Shuriken) is all Naruto. So in essence it is still all him.
No boy, CM is the same thing, by orochi giving it to him is complete different than already having it. That's why it runs out because its not his. Though it is also like sharingan completing his jutsu its still entirely different by being natural energy.