Gift cards are digital by default: WithWine emails the customer a PDF. If you also want to sell printed gift cards that you post to customers, set up a separate gift card product that requires fulfillment.
How Requires fulfillment works for gift cards
Digital gift card: leave Requires fulfillment off. The order goes straight through on the Orders screen without needing fulfillment.
Physical gift card: turn Requires fulfillment on. The order is held on the Orders screen as needing fulfillment, so you can print the gift card and post it to the customer.
Steps
Create a gift card for the physical version, for example "Saltbush Ridge Gift Card $100 (printed)". See How to create a gift card.
On that gift card, open the Shipping section.
Tick Requires fulfillment.
Select Save.
What happens next
When a customer buys the physical gift card, the order shows on the Orders screen as needing fulfillment. Print the gift card and post it to the customer.