Apple is separating the new smartphones into its usual low-cost versus high-cost categories, with big differences between the two models coming down to the camera, display, and battery life.
iOS 13 & watchOS 6 Now Available
iPod Touch (a Touch OS X device)
Gizmodo received word that (unsurprisingly) the iPod Touch runs exactly the same applications as the existing iPhone. According to their contact the iPhone and iPod Touch "use the same damn binaries".
This means that existing 3rd party iPhone applications should easily be installable on the iPod Touch. As well, there's no doubt that someone will try to move the iPhone's Mail application to the iPod Touch.
Apple's introduction of the iPod Touch extends their new Touch OS X platform into another iteration. Unfortunately, Apple has yet to officially open this platform up to 3rd party developers. Meanwhile, there have been major strides in unofficial efforts to bring 3rd party applications to the iPhone. Despite all their progress, without official support, users still have to deal with data loss possibilites with each official firmware update.