Does "storage" mean the storage used to store the definitions of flows? The caching of task state? Eventual results? If it's more than one of the above, in particular if it's both the eventual results store and the flow definition store, then how can I separate those?

Storage is solely for “where is the Flow stored” and the agent will pull the Flow from storage when it’s time to execute. Task results are stored as Results so these are entirely decoupled. Task caching is also a separate thing. Caching is like a flag that just says “don’t even run this task and fetch the result instead”