This is regarding what project preset to use in Premiere Pro 1.5.

My source is standard miniDV NTSC 720x480 in widescreen mode.

My final video should be 640x360, 16:9, 1:1 Pixel aspect ratio for YouTube.

Should I be editing in the widescreen preset? Or should I be working in a custom preset where I go to the custom tab and select "video for windows" and entering a frame size of 640 x 360 and pixel aspect ratio of 1:1?

I ask because I was working in the widescreen preset today (NTSC, 1.2 pixel aspect ratio, 720x480) and had two videos in the timeline (one video is from a digital camera not widescreen). I then scaled down the dimension of the widescreen video so that both videos can fit side by side in the video frame. I left a small gap between the two videos but after encoding I played the video in Windows Media and Quicktime and the gap was gone. I am assuming this occured because the pixel aspect ratio went from 1.2:1 to 1:1 when the video was encoded.