1. The distortion that is sometimes apparent is cause by the glass panels flexing slightly as the external air pressure changes, and in doing so compresses the Argon gas inside the unit. It's far more noticeable on large units, such as those used in patio doors.
2. You are allowed to drill holes - you just have to take great care not to let the drill tip run into the edge of one of the toughened glass panels. If it does, the panel will shatter into thousands of tiny fragments.