2. If I draw objects offscreen using the DrawImage command am I right in assuming that nothing will actually happen
Nope, sadly. I've tested this in a realtime environment - drawing thousands of images off screen will result in a hit. Simply wrapping the drawimage command with soemthing that calculates whether the image is in visible boundaries gave me a 100 fps boost.
Seems to me that something like this should probably be added straight into Max2D really.
I did some stress tests a while back and there was a slight performance increase if you recognized an object was off the screen and didn't render it. But it was slight.
My program suffered a ~20% decrease in speed, I wouldn't call that slight.