Alot of misconceptions on here already, not surprising though.
Some of the better vinyl plank flooring is 100% waterproof. Just test it like I stated earlier. A good company will back up their products.
You can cut vinyl plank with a flooring saw but it means multiple trips outside to cut if you want to limit dust.
A good quality vinyl plank cutter will save install time by 40-50% and no dust. Well worth the price. You will have to lengthwise using a saw on edge planks.