it won't be thin out after NST, but dries out alot
the major differ between "NST" and "cream straigther" is NST wouldn't takes too much moiusture out of the hair strand, and it keeps hair look shinny and healthier.
usually the stylist must trim or actually change a bit the style for you, because the total texture of you hair and style are changed by the perm, and of course he/she should cut off the split-ends for you i am sure.
well i couldn't tell which is the best in tai po, sorry mate