Is the 30 mil wear layer worth it over a 12 mil plank?

Yes for busy homes. A 30 mil layer is rated for heavy commercial traffic, so it resists scuffs and dulling far longer than the 6 to 12 mil layers on most residential vinyl. It is the main reason to pick this over cheaper planks.

Can it go in a basement or bathroom?

Yes. It is 100% waterproof and rated for above, on and below grade, so basements and bathrooms are fine. In wet rooms, seal the perimeter and wipe up standing water rather than letting it sit at seams.

Does it need underlayment?

No. An IXPE pad is attached to each plank, so a floating install goes straight over a flat subfloor. Adding another pad on top would make the floor too soft and stress the locking joints.

It floats with interlocking joints or can be glued down directly. The rigid 12 mm core needs a flat subfloor, typically within about 3/16 inch over 10 feet, so check and level first.

How much floor does a carton cover?

Each carton covers 17.96 square feet. Add about 10 percent for cuts and waste, more for rooms with many angles.

Will the long planks be hard to work with?

The 72-inch length means fewer seams and a cleaner look, but the planks are heavy and awkward for one person. A helper and a tapping block make the job easier.