We have ecommerce website for multiple stores so seller can connect PayPal by themselves but sometimes they don't know how to get credentials/key, so is there any way to use PayPal email instead API key?
I am using API credentials, but I want to use PayPal email to make it simple.
To set up a simple PayPal checkout for intent:capture payments, you can set a payee object when creating the order. See pay another account for examples.
Other operations will require either the seller's Client ID and Secret, or permissions for a third-party integration.