J805
2
I just did a quick test for you.
Here are my findings.
When you choose ‘Update existing subscription’ it just replaces the subscription each time so there is always just one. So referencing Current User’s Stripe Customer Subscription and Current User’s Stripe Customer Subscriptions will be the same value.
When you don’t, however, it will put the Current User’s Stripe Customer Subscription as the most recent subscription but will have both subscriptions in the Current User’s Stripe Customer Subscriptions list.
Does that help? 