I really like my Adidas boxer briefs. They don't ride up, bag, or sag. And I don't have to wear a harness or use adhesive to keep my packer in place. The waistband does roll down below my muffin top, but I don't really notice it.
Basically, you wanna find something with at least 5% spandex. 100% cotton with stretch out, ride up, roll down, wedgie, all that. Even if they say they don't ride up, since cotton doesn't stay snug, the legs with stretch and ride up.