In my experience with the system, when you schedule a group, it only goes to the DMPs in that group. The sub-groups aren't actually part of that main group, so if you have a DMP in a sub-group that isn't listed in the main group, it won't receive the presentation.
That being said, it's not a bad idea to organize with sub-groups, so that you can segment your messaging when you need to. You just need to make sure that all the DMPs you want to schedule are listed in the specific group you are scheduling.
Protip: If you are scheduling a main group and a sub group at the same time with different content, don't start one a few minutes after the other. If any of the DMPs are shared between the groups, it will be a toss-up which content they will show if both schedules have the same start time.
Example: You have a main group and 4 sub-groups. You only want one of the subs to run separate content, so you schedule that one. If the start times are the same, a split second determines which program they show, because the sub-group DMPs are also listed in the main group. By sliding the sub-group start a couple of minutes later, you guarantee that they will receive that command and display the alternate content. Alternately, you would have to schedule all the sub-groups individually, with 3 of them running the same presentation and one running the alternate.
