The sage of the six paths, have learned and trained everything on his own.
But he wasnt not only powerfull, he was a good boy (more than tobi xD)
You cant compare him with naruto or kabuto because of the 2 different sage modes.
He has all of the six paths, that not only mean that he can controll all elements, its everything, see at google; spiritual flows of nature, the 6 paths are the main grps of all being.
But what i can say, the personality of naruto, its similar to so6p and that means the true power.
Back to the topic,
He had no study with someone, he was the first to realize that flow of nature.
And the sage itself, is a title.
Naruto is the sage of the frogs nature flow,
Kabuto is the sage of the snake nature power,
But so6p is the sage of every nature power and flow.
Good question!
I hope this clears it a little bit