Welcome to the forum.
The Signature Strat are the production version of the Custom set. The Custom set is sold out, you can't get it anymore, unless you find it used. The Custom set came in a signed box, wound and signed by Seymour Duncan himself. Production version is wound on the shop floor by current employees who make all the pickups.
I believe originally the loaded pickguard was offered in two versions: one with standard stagger and normal tilting bridge pickup, while the "voodoo" version had reverse/left-hand stagger and the bridge reverse-tilted, like a left-hand strat but in a right-hand pickguard.
Now I only see the Signature loaded guard with reverse stagger and reverse tilting bridge pickup available on the web site. Be aware you will need to make sure your guitar is routed to allow a reverse tilt bridge pickup.