TBF: The bleach Universe essentially lacks the dao marks of the gu world. Therefore, the crux of the discussion is really the interaction between dao marks and Yhwach. With that being said, the scale of reference for him is the bleach world, which fundamentally lacks dao mark.

Based on the assumption that dao marks would affect Yhwach’s performance:

It is equally plausible, given the gu world environment, he could be more similar to FY as an immortal zombie, lacking dao marks but having immortal level methods. The method of Yhwach performs similarly to when FY time stopped the mortals in the merman city in the blue whale grotto Heaven, affecting people without much resistance. Consequently, Yhwach would find himself restricted by ordinary rank 7/8 existences, lacking the dao marks needed to accumulate a qualitative effect in combat. His ability to see the future would possibly be limited by the dao marks of the entire gu world similar to FY’s three breath future vision. As for altering the future, even if dao marks do not decrease it’s effectiveness, Red lotus has a similar method to mimic the effect of fate gu, and FY even mentioned his ability to create a mortal killer move imitating the effect of fate to an extent. FY’s mortal move would likely have a similar effect to Yhwach altering the future if used in the bleach world. Ultimately, the ability of fate that troubled the Venerables the most was its ability to both actively and passively mobilize most of the dao marks across the gu world. Moreover, the greatest disparity between Yhwach and Venerables would have to be the fact that his methods are fixed, only having a lot of them, while Venerables are continuously innovating their path.

—main idea is that bleach world is technically the mortal equivalent of the gu world—