First off this is an excellent question that I don't believe we are ready to comprehend, although the answers are indeed in the science itself. Most digital assets are left in the "cloud" of digital information. It is backed up consistently to hardware, where it can be accessed by its owners using a digital key that never has to touch any network. So to answer, which OS is controlling web3 is to simply remember that the block chain is a decentralized and more cryptographically secure method of not only peer to peer transacting , but also proof of digital ownership. Understanding that these are digital assets, the OS will change, owner to owner. The digital ledger gives validity to which OS will govern it. And that's the beauty of web3.