Hey BLUE;
We used to have to build different folios for iPhone and iPad back in the previous version of DPS (DPS 2014.)
In DPS 2015, the differentiation is more about phone and tablet, rather than specific devices (or platforms) it's about device classes.
If your project is setup with two top-level nav systems (Project Settings) then you build collections and collection content for both phone and tablet. And the organization in the phone structure goes to all phones, all tablets get the tablet structure. These structures might have differently design/exported content for the two device classes if you're working with pixel-perfect content, or one article using HTML/CSS could be loaded into both structures...
All pixel-perfect content will scale to fit any screen, so a layout designed for phone will scale to all phones regardless of OS/manufacturer. An iPad sized design will scale to fit all tablets. Phablets might get one or the other depending on how the device identifies itself -- and then it'll scale the content.
HTML-based content will fill the screen, and if you include CSS/media querries/etc. it can adapt to the device size. Greater flexibility, perhaps less interactivity depending on your HTML skills.
There's a different approach in DPS 2015.
HTH -- Colin
