Hmm... regular audio is the default sound, but nonetheless you can always change it by hitting the "audio" button on your remote until track 1 (rather than track 2) is selected.

If your PS2 is stretching it vertically, what its really doing is NOT compressing it vertically. If your TV is 4:3 and your PS2 is set to 16:9, its set wrong. You want it set to 4:3, doesn't matter whether its letterbox or pan & scan since all that does is decide which version to default to if a dvd has both letterbox and pan & scan versions. Since no DVDs will bother cramming two videos on one disc these days, doesn't matter what its set to.