Nylon = Bad. Stretchy
Polypropylene (Polypro) = Good. This is what Ed Speer sells.
Polyester = The best. Low stretch, high breaking strength, and very abrasion resistant.
Webbing is kinda overkill for hanging a tarp. Just use some lightweight, small diameter line. There are several thread here that go into detail about the different types of webbing. Just do a search
“Light thinks it travels faster than anything but it is wrong. No matter how fast light travels, it finds the darkness has always got there first, and is waiting for it."