If you migrate from a earlier release, it’s possible to plan your deployment to the latest BIS-F release. The ADMX uses the same values under hood as earlier versions, please have a look to the list of Deprecated Features to check which features are removed
From a Best Practices view you can replace the ADMX in the PolicyDefintions as described in the GPO Configuration. The existing BIS-F configuration let it untouch and create a new BIS-F Policy to prevent issues in the existing environment.