What this video covers
The Basics step of a subscription option, Billing & frequency: the four ways customers can pay (Pay as you go; Prepaid, auto renew; Prepaid, one time; Prepaid, separate orders), Billing frequency and Deliver every, selling Prepaid, one time as a gift, the Selling plan ID, and what shoppers see on the product page.
In short
Pay as you go: customers pay for each delivery when its order is created, until they cancel. Prepaid, auto renew: they pay upfront for several deliveries, then again after the last one.
Billing frequency is how often customers pay; Deliver every is how often a delivery ships. Billing every 6 months with a delivery every 2 months means 3 deliveries per payment.
Prepaid, one time ends after the last delivery. Only this type can be sold as a gift, and only on a new option: tick Sell as a gift (you can't change it after saving) and turn on Shopify's Subscription Validations checkout rule before you sell gifts.
Prepaid, separate orders: customers pay upfront, and each later delivery gets its own $0 order. Each charged order costs the product's price once, so price it for all the deliveries. Only a new option can use this type. A greyed-out card with a plan name means your Appstle plan doesn't include it.
Switching how customers pay turns off what the new type can't keep (the trial, the cancellation minimum and end, the fixed billing dates, the later discount), and switching back brings it back. Check How it works, on the right, then click Done and save the plan.