Preheat smoker to 225°F with hickory, oak, or pecan pellets. Clean and oil grates.
Form ground beef into 4 patties (8 oz each), ¾-inch thick. Season both sides with salt, pepper, and garlic powder.
Smoke patties at 225°F for 45-60 minutes until internal temperature reaches 135°F (medium-rare) or 145°F (medium).
Meanwhile, fire-roast jalapeños until charred. Remove skin and seeds, then dice. Mix with cream cheese, cheddar, bacon, paprika, and salt.
When burgers are 10°F from target temp, increase heat to high or transfer to hot cast iron. Sear 1-2 minutes per side.
Top each burger with jalapeño popper mixture during final minute of searing. Toast buttered buns until golden.
Assemble burgers with desired toppings and serve immediately.
