The Byakugan actually does, look at Sasuke vs Naruto in his
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Then look at Neji vs Naurto in his same state.
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On the page before, it showed that Neji unlike sasuke saw the attack coming, it took 3 tomoe Sasuke to even avoid and counter his moves
Naruto was in a higher state of the Kyuubi mode when he fought Sasuke. He had protruding canines, Slits in his eyes, and sharpenend nails. none of which were present in his fight against Neji.
Naruto's own base speed also increased from the exams to when he fought Sasuke. Your theory of Byakugan giving the user a piercing perception when in a Sharingan type fashion is false. The best you could pull from those panels is that Neji was faster than Sasuke, but as ive already explained thats untrue.
gentle fist disrupts
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Neji literally puts his chakra into kabuto which will obviously mess up Kabuto's chakra to the point where he can't even form chakra properly.And you thinking Kabuto can keep up with Neji's speed is also a 'speculation'. You said it yourself that Kabuto isn't good at CQ so why deny it? And rasengan still messed up Kabuto cause he collapsed right after proving how futile his back up plan was.