Probably, but the Inkyphat is a low power e-ink display, meaning it isn’t very bright, unlike your standard LCD or LED screen. The screen looks an awful lot like paper rather than a screen, so it’s hard to penetrate plastics.
Not at all, as long as it’s perfectly clear. The low-light levels simply means it is more likely to diffuse and smudge together through various mediums (as far as my knowledge of physics goes).