ISO are a bit like patient, they look for the highest attacker/defender discrepency and try to use it, so if for example the opposing team has 1 excellent guard (#1) and 1 only decent (#2), the offense will prioritise the guard playing against #2.
It's a bit like when you use patient with a guard at the C position, but you don't have to use a player such out of position (that helps for rebounds for example, a guard@C will always be out rebounded by the defending C)
Motion or PtB are more neutral like you said, they don't really look for the highest discrepency between attacker/defender, they just move the ball until they find a decent shot. I don't really like motion for our U21 because we don't really have excellent outside shooters (jump range is low), and it tends to yield a very large number of 3s (look at Uruguay for example, almost half of their shots where 3s)
Uruguay does not really have "holes" in their lineup, so I let the GE choose which ouside player had the best shot.
Again, it nearly worked, we were ahead most of the game, and only 4 points behind 60seconds from the end. With equal enthusiasm we would have won. We out-rebounded them badly, had more assists, it really was a close game. Could we have won with other tactics? Certainly and that pisses me off and I'll adjust for that in the future, but I still haven't found a "magic" tactic for this team