Rockbox is a software that runs on several players. For the most part features are identical, or nearly identical, unless the hardware can't do it.
Think about a single version of Windows (say, 98SE for this example.) You can run Windows98SE on a laptop, or a desktop. It can be a Dell, or a Gateway. Almost everything will be the same. Maybe one can't play DVDs because it doesn't have a DVD drive, but that's not really a difference of the Windows on each, but the hardware.
The same thing goes with Rockbox. The controls work the same, the features and functions work the same, with the differences being that sometimes it can't do something just because there's no hardware to do it.