Lew,
I can't answer your questions regarding insulation....i never really
thought about it. you can try hardwoodinstaller.com or diyflooring.com
for some answers. Or, if you go to a flooring store in your area they
may be able to answer that question. There are several different types
of underlayment ranging from foam padding to a fiber similar to felt,
to cork. The better the underlayment the better the noise insulation.
There are not many negatives to laminate, but one of them is the sound
(they sound hollow) so better underlayment helps that and its not
really that expensive.
Al