1. I’ve had trouble getting Jami to work at all, I think because of incompatibilities between versions and whatever. You might have better luck with something like Linphone.

2. I haven’t tried a VOIP hardphone but I use Linphone on Android sometimes. I would say call quality is worse than normal cellular voice calls even those are certainly VOIP at some level too.

3. VOIP is more crap to fool around with and periodically troubleshoot, but you can get it to work if you have to. I don’t find landlines to be worth it any more (I just use mobile voice) but they’re probably still the most reliable of the approaches, and I guess it depends somewhat on your family’s discomfort level with technology.

VOIP hardphones sound nicer to use than mobiles, but I guess unlike traditional landlines, they don’t work in power outages. All the ones I’ve seen rely on a power cube.