Ingonimania It's not a problem, sandboxed Google Play Services installs on GrapheneOS without special privileges, allowing you to use the official versions of Play Services in the standard sandbox, unlike the original operating system where Play Services has privileged access to the device.
Curve Pay is a proprietary app that is not available outside of OEM stores such as the Google Play Store, so you need to install Sandboxed Google Play if you want to use Curve Pay.