What to Serve Along With the Buns?

If you want to stay on theme , make these.
https://food52.com/recipes/21537-spicy-korean-style-gochujang-meatballs
I would make a thai cabbage slaw. maybe a nice lo mein or other noodle dish.

First, all praise for this ambitious undertaking!
As the buns will take time, dollars and energy to source and make, I'd make them the star of the menu and go easy on yourself for the rest of the dishes.
Depending on your guests' tastes for traditional or unconventional, American and/or other national cuisines (and, again, your time and resources), go for a buffet of Super Bowl party favorites (see link at end) or some take out Korean items (kimchi, ramen, cookies or other dessert).
https://www.thedailymeal.com/entertain/most-popular-super-bowl-party-foods-ranked-slideshow