That's really interesting. I think that in both cases, those features normally should work without pegging disk all the time. I think that you're encountering a malfunction of some kind where turning off the services gets rid of the symptom, but the underlying root cause isn't fixed (whatever that is).

I could imagine a situation, for example, where some kind of settings which control those features are corrupted and cause the features to go crazy.

For instance, superfetch somehow get set to try to prefetch all files instead of just a selected set. I wonder how superfetch decides what to fetch, and if that's governed by a file somewhere on disk, and if that file is corrupted.