The Kobo website
states: 5” E Ink touch screen; Vizplex V110 display; 16 level grey scale.
If you look at that eink.com website and have a look at what they say about the Kindle Paperwhite, Kobo Glo and Kobo Mini, at the very end of each bit it states "Uses E Ink Pearl Active Matrix Display". But I don't think they all use the same display? Maybe they are all pearl, but the vizplex is a different grade?
As for the plastic mentioned in the screen, I really think there's probably a plastic layer, but the screen underneath is still going to be glass. There is no way they wouldn't have made an awful lot more out of it otherwise.