I am not sure there is a context in Nietzsche for the concept of hubris. He uses words like 'excessive' or 'overweening' to describe aspects of a real thinker's personality, and those adjectives are sometimes applied to pride, but the sense remains positive.
Most pointedly, in the Gay Science he complains how his poor health and this overweening spirit and pride are at odds, wearing him out and wearing him thin. The image I get is of an overly energetic child or pet that is purposeful and amusing in going beyond what the parent or owner would choose, or even what he can easily tolerate, leaving him taxed for his own good. He seems to gratefully rebuke them for their inconsideration and their refusal to let him be an invalid.
Discussing Wagner, He has much to say of the overuse of noticeable excess as a symbol of power (the force of the vibrations, the intricacy of the melody, etc.) which represent false self-evaluation. But this is not about power itself. It seems to be linked more to a sense that it does not represent the real pursuit of art, and instead compensates with false impressions and distractions or cunning manipulations.
Wagner is vain in the proper sense of the English word, but it is not hubris in the Greek sense, as I see it. It is the giddiness of being flattered, and the willingness to be shaped toward more flattery. He just does not know where his honest power would lie, and how much kinder and more edifying he could be to his audience if he found it.
It is hard to see where he thinks anything that truly arises from within can be bad or limiting, including the natural childish narcissism that bases vanity. One can fail, and one probably should, but learning to expect failure does not fit on the agenda for a powerful spirit.
At many points in the Genealogy of Morals it seems that in some sense, one's own sense of one's own value is never wrong. Those who devalue themselves become useless and parasitic, and those who do not bring forth their genuine will, which creates opportunitY. Those who misattribute their value to some cause are truly mistaken, but it is about that cause and not about the value itself.