You can't tell if they will be fluffy or not. As the kitten gets older it will get easier to tell if the kitten is longhaired or shorthaired, but in very young kittens it is very difficult to tell.
She will act very weird and may bite and scratch. She will also look for a quiet dark place to bed down. But believe me, you will know when she is about to give birth.
Keep the kittens and the mama safe and warm. The mama should allow the kittens to suckle her milk. If the mama is especially exhausted you need to make sure all the kittens find their own teat and...
A cat's gestation usually lasts and average of 63 days, but if you do not know when the mating took place, it is difficult to tell. Many cats will become very affectionate and clingy - some do not...