[alsa-devel] plughw vs default / per-application volume changer

Hello, I am new to ALSA and I cant figure out 2 things.

a) if and why should I prefer the "plughw:0,0" over the "default" device name. I am developing a simple audio player which is based on the latter. I made this choice because when I was using plughw:0,0 with other audio programs(flash player,vlc) open in the background I would get the "Device is busy" error code. With default, it's fine.

b) can I have an application specific volume changer? So far I have managed to tweak the master volume of the "default" device which has a global effect. Im guessing a) and b) are connected.

Thanks for your time