Hello,
The Paypal recurring plugin is using the same API than the HikaShop paypal (classical) plugin.
That API do allow to create a subscription and receive notifications regarding its updates ; but the API do not have the access to cancel a subscription ; only the Paypal dashboard will propose that.
When a customer ask for the cancel of a subscription, he should see a message telling :
PAYPAL_RECURRING_CANCEL_INSTRUCTIONS="You need to login to your Paypal account and cancel the subscription in the preapproved payments"
Paypal REST might be able to create subscription and handle the cancellation via the API too ; but for what we saw, it requires to create the plans and subscriptions directly in the Paypal Dashboard (or use the API to create them).
That Subscription API do have the same limitations than the Stripe API ; thus the same reason why we are not fan regarding an implementation which would generate a lof of restrictions (and potentially bugs) regarding the way than customer could buy subscriptions.
Regards,