Baker's malt extract is different from brewer's malt extract. I think you can use the brewing stuff for baking, but not the baking stuff for brewing. That said, I suspect a light malt extract would make a basic, classic pretzel, while you would get darker pretzels and more complex and roasty flavors from darker malt extracts. Approach the pretzels like a beer recipe and you should be able to control your output in a similar way.
Primary: RIS 1.1
Bottled: RIS (黑墨), I Can't Believe It's Not Bitter! IPA, Caramel Amber Ale 1.1, Osmanthus and Sichuan Pepper Saison (桂花花椒赛森), 米酒 (rice wine)
Coming Up: Imperial CDA, I Can't Believe It's Not Bitter! IPA 1.1