Blizzard Balance Overwatch $20
UNLOCK SKINS, EMOTES AND MORE!
Works like Battle.net Balance
Blizzard Balance can be used to buy Overwatch Loot Boxes or other items and games from the Blizzard Shop. Each Overwatch Loot Box contains four items that allow you to customize your Overwatch heroes on PC with Skins, Sprays, Highlight Intros, Emotes, Victory Poses, Player Icons, Voice Lines, or in-game Credits.
For Xbox just buy an Xbox gift card, https://m.gamestop.com/product/console-currency/20-xbox-gift-card/111820
Yes I think you can after you punch in the code you receive, it should allow you to purchase the game through your new blizzard balance. I hope this helps! :D