I'm assuming that the "144 or 192" is based on 48 minutes/week, correct (i.e., no bonus for going over 48, some penalty for being under 48)? This would mean somewhere in the neighborhood of 3-4 weeks...?
Exactly right. 48 minutes per week is the perfect amount of training. Any less and you don't get full training. Any more and it doesn't make a difference to training.
The information I had gathered thus far on the forums suggest that the fewer positions being trained, the faster the training speed. For example; training C/PF is quicker than training C/PF/SF (for training types such as Inside Defense), and training Rebounding for C/PF is faster than training Rebounding for the entire Team.
Like I said there are many factors I just listed a couple off the top of my head, you always tend to forget something. And yes training less positions provides increased training. We are not sure if training 2 gives half the training to each player or some other way.