To start off, I'll just say that Ohma's predictions and Mori's instincts should cancel each other out nicely. Ohma is capable of predicting up to 100+ moves ahead and resisting predictions up to that level, while Mori's instincts allow him to react to Massively Hypersonic characters while he was a baseline subsonic character. Ohma will be able to handedly predict Mori while Mori will always be reacting.
But that doesn't mean Ohma doesn't really have the advantage anyway. Being able to know pretty much all of Mori's moves, even if he'll react to them, is still pretty busted. And even worse, he'll know that Mori will react in the future, allowing him to account for a wide variety of moves before they even happen, something Ohma should be able to do with his wide variety of skills through the Niko Style.
Speaking of the Niko Style, Mori copying it may not be much of a problem, as Ohma knows how to counter and account for the Niko Style, he's been trained in it his entire life and knows its weaknesses and advantages, and how to optimize and use its skills effectively, even when it's used against him.
But even if he can counter the style, Mori will also be able to counter. As stated by Ovens, Mori can adapt to new skills in mere moments, can capitalize off of them, and can counter being martially stomped multiple times over. He's been shown to be able to jump multiple tiers with the techniques he comes up with, and can create techniques that one-shot previously comparable opponents on the spot. This will be Ohma's main problem.
Mori is going to be constantly adapting to Ohma's moves, but Ohma will ultimately always predict it, but that won't stop him from being overwhelmed strength wise. He's always going to be the lesser in terms of AP as Mori will always be growing. Mori can paralyze him, cause his limbs to explode, cause him pain, and all that good stuff and more and shit. Ohma's going to predict all this, and he's going to be able to account for it until Mori overwhelms him. He's a smart fighter with amazing kinetic vision and experience Mori just doesn't have, and being overwhelmed is something he's familiar with. Everything Mori can do will fall within the scope of Ohma's experience, as he simply predicts all of Mori's moves hundreds of times over while Ohma is unpredictable to Mori.
It's a close fight. But Ohma has most of the advantages. He has the skill and experience advantage, he's a better all around martial artist, has better, way better analytical predictions, can generally counter anything Mori can copy through his experience, and is no stranger to being outdone strength wise. It'll be tough, Ohma won't come out unscathed. The amount of adaptation that Mori possesses is simply something Ohma won't be able to deal with in a long-running fight, he'll be overwhelmed physically, and he'll be injured, but in the end all he has to do is not get hit, which is well within the scope of his abilities as he can always make distance with a variety of techniques. Ohma is just the better fighter.