Breakout Room Question

Will we be having three board of directors specific meetings next week. The first meeting will start at 1:30 pm, the second at 2:30 pm and the third at 3:00 pm. Instead of giving each of the meetings their own unique meeting notice, and requiring the participants to log into 3 separate meetings, is it possible to use meeting breakout rooms instead? The first two meetings will have a uniquice mix of participants, where as the third meeting will have the full board. Some members are early to the meeting which causes a disruption when they join the meeting. The last part of my questions is if we are in a breakout room and someone joins the meeting that is already in progress, can they hear us in the breakout room and vice versa? Thanks for your help.