Quality film thickness =

Once well established, it is forgotten: no loss of sensitivity. zero bubble.
It does not apply to the edge because the screen is curved around the edge. I think this is intentional (it would eventually take off the film.)

For the "champions" of the pose, I recommend an infallible technique advocated by BodyGuardz and valid with any movie:
Wash your hands properly (soap rinsing)
properly clean the screen of your smartphone.
Spray on your fingers on the screen and on the film to stick, deionized water (the one for the iron Madame).
You can position / reposition the film before expel the air and water with the small scraper provided.
The water will remain under the film evaporates (yes) within 48 hours and the film is then perfectly laid without bubble is free of dust.

Good order and good pose to you.