The Graphtec CC330-20 and the Silhouette SD are the exact same machine. The Silhouette SD is just a rebrand of the original Graphtec hardware for the American scrapbooking market.
The CC300 (what you refer to as the Lite) is useless. Without the ARMS eyeball, you can't do a print-and-cut.
Since I'm the guy who got WWG up to speed on machine-cutting, all of the information on this page applies to WWG too:
http://www.ebblesminiatures.com/shop/machinecutting.php
I posted the above on this forum too, but somebody forgot to sticky it here.
US Letter and A4 are not a problem. The standards that I established use a frame size of 7.25" x 9.51", which factors in the narrower width of A4 and the shorter height of US Letter. WWG follows these standards also, but I can't speak for anyone else.
-Mel