I
updated the character chart with pics of the seiyuus.
And it seems that the male manager used to manage the first group of idols, since a couple of them show up in eps 2-3 and say how much they liked him being their manager. But the whole emphasis of the show appears to be on the third group. The first two groups are what they are trying to achieve.
As for real idol groups, I don't know much, but here are some videos from YouTube:
Morning Musume, the longest-lasting group, which keeps renewing itself with new generations of members.
Berryz Koubou, a very young group (average age 12 in that video) who can just about sing and just about dance and are quite entertaining, especially if you judge by the chanting, jumping fans in their concert videos. The shortest one, called Saki, is their "captain."
Robo Kiss, with appendages hanging off them that are not quite ribbons.