Co-Managed and Intune Enrolled co-existance

Hi Guys, I'm trying to plan for a scenario where we have a standalone SCCM instance managing around 1000 devices, and Intune managing around 100 devices.

What I want to do is Migrate 900 of the SCCM managed devices to Intune only, but the remaining 100 devices will need to be in a co-managed state (Images deployed via SCCM, but policies managed in Intune)

What I'm struggling to understand is the MDM Authority. I'm assuming because 100 co-managed devices will be in play, i would need to change the MDM Authority to Co-Managed.

However after changing the MDM Authority will the other 1000 devices be able to be managed directly in Intune? And will I still be able to enroll further devices into Intune only?

Thanks in advance