Unless Borders is very different from Kobo, they do not have to create an account for you--you do it yourself on the Borders website. The Kobo associated site in NZ is Whitecoulis, right? You can
download their desktop--or the Kobo one, or the one from Borders, but you can only sync with one of those Kobo associated accounts. Use the other stores by downloading the purchased/freebooks as ePUB using Adobe Digital Editions. Be sure to use the same login information on ADE and for all of the bookstores you will use with Kobo.
With the WiFi edition, you will get your firmware updates over the air when you ether shop wirelessly or update your library wirelessly. The desktop application updates through the desktop application.