Can anyone recommend a PayPal payment plugin that works within the ROPC plugin and only creates an order after successful payment?
The default Nop Paypal Stardard plugin creates an order before taking the payment, which will reduce the stock quantity without payment.
You basically need a payment plugin that does not make a redirect.
So that it allows the customer to enter their credit card details directly on the checkout page and if the payment is not successful i.e wrong credit card numbers etc. then the customer will not be able to place and order at all.
Most PayPal plugins i.e PayPal Standard uses a redirect to the PayPal site which requires the placing of an order. You can try any PayPal plugin that does not require a redirect i.e PayPal Direct. But as far as I am aware PayPal will stop the support for their API later this year and they recommend using Braintree instead (PayPal bought Braintree some time ago). Braintree is the payment provider we actually use on our own website (Nop-Templates.com) for Credit Card payments along with our One Page Checkout plugin and yes it does not allow the customer to place an order if the payment is not successful.