SO you're saying Kurama madness + 2 weeks of training > sage mode, chakra mode, numerous shadow clones during the war ?
well the equation is flawed because the chakra mode is the by product of Kurama and training
first nardo example you used-Was naruto with minor access to kurama chakra, it would leak out from time to time. then when fighting pain mainly without kurama, the whole hinata thing happened and he pulled seal off. This open floodgates of chakra and rampaging until ghost minato put the gates back up. At that point he beat final path and went to fight nagato, kurama leaked out the as well. Kurama does that when nardo rages to weaken the seal. Still though most the fight was done
without kurama.
Second nardo example- after killer B's training naruto had major access to 9tails chakra. He could control it to a point, he had a tank of ckakra he didn't want empty (amount he took from kurama during training), he used this most of war though kurama started helping when madara's name was tossed out. Later duing his fight with Obtio they synced up pefectly and basically merged chakra pools nardo even opened the seal,
kurama gave nardo free access to all his chakra, to the point of going to sleep to keep nardo fighting (VotE 2)
The Chakra mode is a much more refined controlled version of V.2 (kurama Madness). He has giant ninetails cloak of teamwork, instead of being forcefully transformed by a ninetails wanting control cause nardo's dumbass pulled the seal off