No trio of angels. Usually what ends up happening is
a) Two of the three pair up, leaving a third wheel that gets bullied
b) They're all aggressive and end up picking on each other
c) One bullies the other two, or vice versa
If you wanted a trio, to be practical I would recommend a 55 Gallon with a lot of hiding places. And even then they don't work out. I know there are a couple of people that keep trios successfully (@absolut, didn't you?) but other than that the majority have not.
Angels eat schooling fish that are big enough for them to eat. I would only consider neon tetras to be considered angel food, but even then some keep them with angels no problem. All other bigger tetras that would fit in your tank (rummies, cardinals, black neons, glowlights, etc.) would be fair game with angels.