Most period-havers I know typically have a light flow on their first day as a little warning that the next two or three days (or seven, if you're a REALLY lucky genetic lottery winner) are gonna be basically Noah's First Plague.

After the really rough part of the downpour has dried out, you're supposed to downshift from Super to Regular, then down to Light or just use pantiliners until the bleeding stops.

Most folks use Supers or pads at night, or if they're planning on doing something where bathroom breaks aren't guaranteed, like long road trips or theater performances. Never leave one in for longer than 8 hours. You have a slight risk of developing something called Toxic Shock Syndrome where a sudden explosion of bacterial growth can send you on a potentially one-way trip to the ER. (Not very likely, literally 1 in 1000 odds. But 0 sounds pretty good to me, so I never leave them in for too long.

Size does NOT matter here, capacity does. And so does application. Every tampon will absorb moisture, but if you put in a Super on a Light day, it can lead to some seriously uncomfortable dryness. Everyone has their own preference for brands and type, since some may have ingredients (like fragrances or residual cotton pesticides or certain kinds of plastic) they're allergic to. Or, y'know, boycotting Unilever or Procter & Gambel is also pretty based.

If you're asked to pick up a box, the person issuing the fetch quest will make those specifications for you. If you wanna score extra points on the quest reward, ask them if they want Midol too. It's usually in the pharmacy section, roughly in the same area as Aleve and Tylenol.