1. Each deck is fixed. However, there is a 1/6 chance for a signed card in the deck replacing the same card.
2. Two decks are required to play the game properly.
3. The Official English distributor has great english resources:
http://www.heartofthecards.com/ws/. They even have printable card translations.
4. Based on the WS cards I own, they are printed on thick card stock (ie. better than standard playing cards). I'd argue that they are slightly better than MTG cards (I play a lot of MTG in my spare time) in quality, however, they are more expensive.
I would like to note that there are even three English deck releases that I know of: Madoka, Fate/Zero, and Disgaea. The Madoka and Fate/Zero decks come with promo cards if you order here:
hammergirlanime.com
