I think it's just best to think of Omniarch as just simply you having lordship over all knowledge which means you have access to it which can translate to being all-knowing. You can reshape everything passively and directly at the same time and it should give you awareness over all things since you're the ruler of totality which means you have awareness over the various universes that operate on different laws such as 2+2=8 or time itself flowing differently like an apple aging faster if it was stuck in that universe or it's composed of an entirely alien liquid that tastes better than chocolate or "water" transforming anything into more of itself or stone made of dreams that can manifest your desires into existence. The other universe could even function off dream-logic behaving differently from ordinary reality. There's no scientific way to understand your power since it breaks the known boundaries of what is impossible but you could try though. You can manipulate material not even made of atoms but something else entirely which could be cubes or something abstract like pain. You have power over universes where the boundary between fantasy and reality is non-existent where the two are one and the same, basically you know that line that separates the realm of desires even if they are nonsensical or illogical and where ideals which are your version of perfection exist and even all the fantasies you had well on the other side of that boundary is the cold dull boring world of science , reasoning and cold hard truths and that boundary between the two is non-existent making a unique universe where all your fantasies become real and where stuff like distance and space along with time lose their meaning with even the environment changing into something else like your old memory of school or a beach or even both at the same time. They could also be an endless limbo-ish labyrinth of empty office rooms that you can get to by no-clipping out of reality and they can also be psychological torment zones that torment you with solid manifestations of your loved ones and your worst memories and even bring your nightmares to life . Basically you can manipulate all eldritch locations , places that laugh in the face of impossibility and sanity. Basically places that shouldn't exist by the laws of reality, physics,logic and human comprehension. This power is very similar to totality Manipulation if it included absolute command and subconscious manifestation along with meta luck.

@TheDevil7777 How does Omniarch have Subconscious Manifestation? Your interpretation of this power intrigues me, my friend!

Well for starters because you can manipulate anything and everything you can turn the thin air into something from your mind purely by accident since you're basically a god. You can make molecules bond with atoms that pop out of thin air and it could be anything you fear or dream of .

@TheDevil7777 In that case, what differentiates Omniarch from Omni-Manipulation?

Well not much really since both can manipulate absolutely everything, the only difference is the name and the title of being lord and since you have lordship over the concept creation I think it implies something with totality.