As a developer of the Pronamic Pay with Mollie for Gravity Forms plugin, I think this plugin is the best integration between Mollie and Gravity Forms. This plugin makes optimal use of, for example, the WordPress HTTP and REST API. The quality of the code is high, WordPress Coding Standards are strictly adhered to. In addition, Mollie users can count on the knowledge and experience of Pronamic, a Dutch WordPress development company. We are very proud of our support department, support issues are handled quickly and by WordPress developers/experts. If you also want to work with other solutions in addition to Mollie and/or Gravity Forms, Pronamic Pay is the answer. We support many other popular payment providers and WordPress plugins.