If your carrying on, no need for your bag to bag drop. A CRJ or ERJ is small, the A320 isn't small.

As from oversold, just go to the gate when it opens (~1 hour before departure) and tell the agent that you want to volunteer. It is important to remind the agent that you want to keep your original seat if volunteers are not needed.

Compensation question was just answered in the thread below
http://www.flyertalk.com/forum/delta...fered-vbd.html