Honoka - Strong, steady, consistent. Emitsun's actually such a good singer, holy shit.

Umi - Rich, earthy, dark, like a really good coffee/dark chocolate. Totally not piercing, more like a blunt force if anything. Gets real fluffy when she gets high though. Most likely to say screw it and take it lower. Like in her solo version of Aisheteru Banzai at "Maki's solo" around 3:10.

Nico - Most in character? Soramaru can get really low, but you'll never hear it, except maybe in Wild Stars. Can't really describe Nico other than the "Soramaru special".