Currently we have an request at our customer to create recurring orders (subscriptions). I see that EPI supports something like this using PaymentPlans. However according to the documentation this is using the old API's. Is PaymentPlan still supported or is there an alternative new API that should be used to place recurring orders?
Yes, PaymentPlan is still fully supported. You can use the new API (IPaymentPlan + IOrderRepository) or the old PaymentPlan