Plantera Ranged DPS Testing (READ DESCRIPTION)

Flamethrower is your best choice assuming circle strats/standard arena
1: This is better than Chlorophyte Shotbow for the reason that you can not pierce with the bow, and so phase 2 mini plants can harm you and your movement

Megashark with crystal ammo if you play is a tunnel/horizontal playstyle (especially enraged).
2: This is because it performs at a similar level to a max dps Chlorophyte Shotbow, granted slightly lower, but freeing up an accessory slot and archery potion, however it will perform the worse if you do not tunnel as your crystals will not all hit

The Chlorophyte Shotbow with holy arrows is the best option assuming she doesn't move much, or if playing vertical tunnels (Nicknamed OSOGOF by Waffle Time)
3a: This requires archery potions and magic quivel otherwise use megashark.