A couple other notes for your list.
iOS is for Iphone and Ipad.
And I think all Android devices are now using the same Plex app, so Android is for all the mobile players and boxes, so smartphones, tablets, as well as FireTV, GoogleTV, and AndroidTV (meaning the newer Nvidia Shield and Nexus Player) boxes.
And as you have already noted, Plex Web client platforms are listed as the web browser that is used, so Firefox would also be considered a client.platform too. Not sure about that new IE browser, but I am assuming it would just be Edge.
And there is also Samsung and PlexConnect. They are third party apps. PlexConnect is truly a third party app since it is sideloaded. Samsung is more of a official unofficial app. It is official, just not managed/updated by an employee of Plex like all the other official apps.
