2) Or you can use specialty PVC drywall trim, such as the Shower Bead, which bridges the gap created by the flange and provides a clean, finished edge against the tub/shower unit.
To learn more about best-practice drywall, visit the JLC Field Guide.
Avoiding Bathroom Drywall Problems
To prevent a bump in the drywall, don't screw through the tub/shower flange.
To avoid a bump in the drywall and the increased likelihood of a cracked finish (the likely result of the typical view at top), you have two choices: 1) Shim the framing next to a tub/shower unit so that it’s flush with the fiberglass flange and the drywaller doesn't need to screw through the flange (detail above).