Air pressure argument is big dumb unless we’re assuming 20% is far higher into 8-A than anyone else that is 8-A, but then that results in 15% being 8-A too since that’s when air pressure actually happens, which can’t be the case unless the differences between percentages are weirdly different or something, idk.
As for Shigaraki, he should just be around USJ Nomu level, though probably weaker. I argue High Ends bare minimum should be the same. You guys can claim USJ Nomu is an outlier or whatever all you like, but facts are that the High Ends are meant to be superior to it physically. We can claim that he’s stronger than them somewhat simply due to being made to fight All Might, but it isn’t some astronomical distance, otherwise the diagram showing they are superior to other Nomu wouldn’t literally use him as a baseline.