I've only used them as keyboards, so I'm not very familiar with the media controller options, but as far as I can see it's a very easy mode to use.
You can use two of them at the same time, one in each hand, but it probably won't be necessary, you can get to type very fast with one hand.
They are very well supported on iOS. I once plugged one into Windows and it seemed to work fine, but I have not tested it extensively.