wondering whether the US would allow any warship (i.e Chinese, Russian) passing their EEZ, and just outside 12nm territorial waters?
Yes, the US would. In fact China has occasionally sent surveillance vessels on similar missions I think to Guam?
But that's kind of a red herring given China's discomfort with US surveillance and military ships passing within its EEZ is also dependent on the overall deployment pattern of US forces in westpac, rather than only the presence of the ships sailing through China's EEZ.
I'm sure China would be far less opposed to US surveillance ships passing through its EEZ if there were no USN bases west of hawaii and no USN presence within the first island chain.