I've been using a UT-72 with an AT778-UV for more than an year now and have not had any problems. I almost always get good reports. When I don't get a good report, there is usually an obvious reason like weather, distance, trees, buildings, etc. This is a very inexpensive setup and I'm quite pleased with it.
LOL! I could have given a better explanation as well.
GMRS is a "channelized" service. As such the frequencies it's allowed to transmit on are hard coded into channels. When in Memory(channel) mode, you are locked down to transmitting on only the approved frequencies and are therefore allowed to transmit. In VFO mode, you have virtually infinite frequency adjustment in the band as Steve indicated. That is why you can only listen in with VFO mode but you can transmit in Memory mode.
The Baofeng MP31 has audio prompts but it is only 2 watts. If you can find a similar 5 watt radio it might suit your needs. Radios like the MP31 that don't have a display are more likely to have the voice prompts you are looking for.
Keep in mind that the ultimate goal is to keep the lightening outside of the living space. And while you are doing that, don't introduce any ground loops.
Some antennas come with that adapter which is nice. The Nagoya UT72/UT72G are such antennas. It's actually an adapter cable. The cable is very flexible and reduces the strain on the SMA on the radio.
The only one I can download now is the "Reference" copy. Can't get the "Official" copy. Not sure what the difference is but yeah, when I download the reference copy it does not have the Line A/Line C restriction.