I did check out stripe. Maybe this is something I should have added in Q. I don't live in US though I am building the app for customers in US and Stripe is not supported from where I am.
I would recommend automating signup so that is seamless . . . but you could have your backend email you for cancelations, etc and do those manually through paypal.
In the beginning keep things simple and be willing to do things manually behind the scenes to keep time/costs low till you have signups and users getting value out of your app that will be subscribers long term.
Payflow Pro by PayPal ($30/mo) is ridiculously complex and it's better to buy an additional 3rd-party service built on top to make it easier (you'd end up paying $100+/month plus 2.9%).