The backing is a matter thats dependent on the size of your spool. Most guys leave half of their old mono line on it for backing. If you can, use a piece of compressable tape on the spool and then backing.
Braid can bury into the larger diameter monofilament. To solve this issue back off on the drag more than you would for regular mono.
The vanish has a reputation for being trash. Its worth the extra money for seaguar
. Its by far the best.