IMHO "Templates" are much easier to use than "Settings Catalog". In Templates the settings are grouped together by functionality and you can see at a glance if the settings are available for ADE/Device Enrolment/User enrolment (supervision is required or not). Settings Catalog does not provide an easy way to select settings wich are related only for a specific enrolment method.
On the other hand it is not obvious if the Settings Catalog uses DDM for all the enrolment method, or only for User Enrolment.
(As per the official documentation it is only for User enrolment: https://learn.microsoft.com/en-us/mem/intune/configuration/settings-catalog)
Finally, is there any information about migrating Templates into Settings Catalog policies? Is it still safe to use Templates if the desired settings are configurable there?
How the migration will take place?