Remote notifications is a special (and rather poorly named) background mode that allows the app to download content in response to a push notification.
From Apple:
The app wants to start downloading content when a push notification
arrives. Use this notification to minimize the delay in showing
content related to the push notification.
Normal push notifications will not require this permission, but adding this mode allows additional functionality for push notifications.
And yes, you will still require push certificates even with this background mode enabled.