However, to answer your question, yes you can buy thicker padding that may absorb a little more noise.

Sure, "blood is thicker than water" and maybe you don't even need the LLC. 

I'd just have them try a thicker weatherstrip like @Jerry Lucker said.

Level 5 (and others, probably) make skimming blades up to 48" wide now, so going from a rough wall to a smooth wall isn't as difficult as it used to be.Skimming should also be cheaper than adding 1/4" drywall because it won't require buying custom sized door jambs (to accommodate the thicker walls), using box extenders for electrical, removing and reinstalling base/crown molding, or any of the other issues you might run into by adding a layer of drywall.

The thicker the wear layer, the longer it will last before it requires replacement. 12 mil is sufficient for most applications.

Cost wasn't that much more for the thicker stuff, the thin stuff felt like garbage to me.

I have been going back and forth if i should put quartz white countertops in the kitchen and bathrooms, some people tell me quartz white does stain one being my sister who recently got quartz in her house- but store owners tell me no quartz doesnt stain and it is the most durable. some people tell me the 2cm is the best and most popular size , but i believe the 3cm is better since it is thicker and can possibly last longer.

You need a solid substrate to hang it from - I think the instructions recommended 1/2" OSB or thicker, so forget about just using it straight to studs.Having used it once I wouldn't go that route again.

Would recommend the thicker the better!

(I have installed plenty of 8mm laminate over felt but this is 7mm and carpet obviously is thicker than felt.)