Can you play more than one sound at the same time?
A1:
Yes. However, you will have to use different sound object variables for each sound.
Q2:
Does it matter to ActionScript what sort of sound compression you use for sounds?
A2:
Only if you compress the sound with the Convert Stereo to Mono option turned on, and then expect there to be two separate channels to be used by a sound transform. Otherwise, all other ActionScript works the same.