This thread has good info.
http://www.picbasic.co.uk/forum/showthread.php?t=5197

As far as the element, depends on the frequency range you will be operating in(sound frequency).

Piezo speakers are pretty limited as to the range. Poor quality sound.

You would be better off with a small speaker. The piezo you picked may not have the range you need. Try one and test in your application. Might be good enough.