Attic - Radiant Barrier

The main question is: What is the attic temperature difference before and after the Reflectix?

What type of staples do you recommend with the install?

What is the purpose of leaving the gap at the eave and the ridge vent in a vented attic? Won't the eave vents still pull the air up to the ridge regardless? Is air circulation required in the area 'under' the reflectix and this is the source?