need some help (if possible)

[rmzV]

i have some questions about program proceses...about dewarp option.. to be concrete and dpi

1. does program at first step dewarping image and then use algoritm to upscale it?
   in that case isnot better to upscale images in another software and then drop them in ST with high resolutions?
2. if i understand correct better to use x2 or x4 of source resolution in output stage?
   or x2 is the best one?
3. i am on photo scaner.. and i measured my dpi (its 192 ) is it ok in that case use 200 in "fix dpi" dialog options?
   or better stay with 192 and then choise 384 at output stage?

please help((