Pal or ntsc

It doesn't matter. It just changes what fps you can set (50 or 60) thus making it easy to get the right rate for broadcast tv.
 
Yes, but that doesn't apply to HD video. Only the frame rate part of it does.
 
There's also an anti flicker setting of 50 or 60htz in the app- from memory, don't have it open right now. Not entirely sure if this should be used in conjunction with PAL 50, or NTSC 60, or if it's a separate setting you can use to clear up the video under certain lighting conditions.