is iPhone NTFS, Fat 32, or Mac OS Extended (Journaled)?

Since you aren't allowed to use it in disk mode, how can it matter?

Don't know the file system used but PhoneView allows to use your iPhone in disk mode over USB.
There are lots of apps which allow to put or remove files on your iPhone also. I suppose the developers of these apps know what the file system is. Try searching for "disk mode" in iTunes app.

PhoneView does have the problem that "resource forks" are lost when a file goes there. Perhaps that is some hint about the disk format? Anyway, to use it for a file where just the data is not enough, archive the file first (SIT or ZIP or something similar that has a Mac compatible mode).