Yes, we use the USB card reader, my daughter uses the family's iPad 4 and it works much as you might expect. The one downside is the need to have a charged iPad when importing a lot of images, the lightning port is taken up...
The P3 gamut is wider than the standard sRGB associated with most displays, not the same coverage as Adobe RGB, it covers more red/yellow and Adobe RGB covers more blue/green, but it's practically nearly as wide a gamut. Still for printing, I'd prefer a calibrated Adobe RGB display. But really I'd be happier with either of them over my current two (very nice but sRGB) NEC monitors.
Rec. 2020 will hopefully put some form of an end to all this when it arrives down at user level...