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

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.