EOS is very thoroughly reasoned out. It's exciting.

I have questions about storage. If block producers offer different amounts of storage per token a user holds, does that mean files are held by only the one block producer that the token holder chooses or are all block producers obliged to hold a copy of stored files? i.e. are a token holders uploaded files distributed across all 20 block producers or only one?

Similarly if there is a custom app that provides its own infrastructure, is that not then just a centralised app? how does the decentralised aspect play in this example? Does the manager of the custom app only hold encrypted data which is protected from underhanded manipulation by them through keys held only on the blockchain? but if so how is the user protected if that custom infrastructure goes down?