Is it true that after a FUE HT person will have "doll like" hair? How many hairs does 100 grafts provide?

You should not be able to detect a good hair transplant surgery.  A bad hair transplant surgery may look like "dolls hair".

if done properly with current techniques a hair transplant should never look like "doll's hair". It depends how much area you need to cover but 100-200 grafts is a very small amount.Our average case is 1800 grafts.I recommend an evaluation with an experienced Hair Restoration surgeon to determine your needs.

it is not true ... I advice you have a FUE; you would get the desired hairline in just one sesssion of dense packing hair transplant.During the placement of follicular units there will be a mixture of single, double and a few triple grafts, which help to create the soft look of a natural hairline. For the first few lines always go for single grafts, later doubles Triples and others.So that a smooth transition will be there giving undetectable hair transplants.

When done correctly in the right hands of a skilled surgeon, a hair transplant can yield a perfectly natural result that will look undetectable. 

Each graft can have anywhere from 1 to 4 hairs each. The average is usually about 2 or 2.1, so 100 grafts would give on average 210 hairs. However it also depends on where these grafts are going- singles are generally placed along the hairline edge while multiples (2s 3s and 4s) are more inward. Similarly, if the grafts are going to facial hair the doctor should be selecting primarily 1s and 2s so that number can be different.
And yes, it can happen that transplant hairs do not blend in well with the rest of the hair. Generally with experienced surgeons this isn't something to worry about but it's impossible to make a 100% guarantee that it won't happen. 

When done correctly;y, FUE removes follcular units which always look natural and never looks like a doll's hair