They both have the same volume and size. The original is a round top Quonset hut design while the Plus-2 is a barn type Gambrel design. The Plus-2 can ship via UPS while the original must ship via motor freight.
Every hoop is placed over and secured to a stake which has been driven into the ground.
As to the amount of heat required, there are so many variables that we refer customers to their state university extension services for the most reliable advice. Because the manufacturer includes a substantial safety factor most of our customers get much longer life from the cover, some up to 10 and 12 years. Construction grade poly which does not have UVI breaks up into pieces in just a few months. Also, dry blowing snow is never a problem, it is the straight down wet variety which can cause trouble.