I have to say, mine are louder than I expected. Especially Periwinkle, when he gets going. He's a shrieker. Honeydew is a little quieter, she just sings mostly. It could be because she spends most of her time upside down, hanging from the toys, whereas Peri is just sitting on different perches all day.
The "volume" isn't too bad, it's just that they are shrill. If I'd spent any time around anyone else's lovebirds, I might have hesitated before getting mine. Only now that I have them, and love them so much, I can't give them up and will just have to deal with it, lol. My hubby wants to shoot them some days, though.
If the house is quiet, they are quiet(er) and just sing. It's sweet. If we all start talking or the TV is too loud, they compete for volume. I read that it's them "singing with their flock", lol.
As for diet, I do seeds and pellets mixed, and give a little fresh food every day. Millet twice a week.