The first picture was of my old herd queen, Delilah. She produced 12# a day at her peak and all through the summer and early fall, when it began to fall off a bit. She was quite a doe. Anyhoo (getting lost in memory lane, here) there are many does who produce mor ethan her, but her rear udder was her strenght, and she also had good side attachments. Her foreudder was pocketed.
The second doe is another one I owned, Firefly, taken of her as a yearling milker, or possibly as a two year old... which is why her udder looks small in that pic. One she matured fully, she was a huge deep bodied doe. These are ordinary working girls, the kind you can easily breed with a little time and care in your breeding program.
For a look at udder ideals, take another close look at the last four pictures, all of National Grand Champions or Reserve Grand Champions. The foreudders extend into their bellies, and the rear udders are high and wide. These does are from the 1980's. They are not perfect, but the fact that they would still be darned nice to have some twenty years later says quite a lot. Many of the ppictures before that era are of goats that I would not want to own, but they were considered really nice for the time.
To improve udders (and in my mind, as long as you're not neglecting other faults, you can't focus too much on udder attachments) go to the ADGA and Missdee's websites and look up the type data for rear udder height and width, udder floor (deep means that the udder is pendulous, shallow can be good if the doe is productive, or maybe she simply has no milk), and Medial suspensory ligament. You want bucks that have a high number of daughters with reliably high, wide rear udders. I have noticed that Nubians aren't as prone to pockety foreudders as Alpines are, so you have that advantage. Do your research and try to find patterns, lines where high, tight rear udders predominate, and get semen from those lines.