Most customizations should remain intact if the UUID is cleared in UDM (see link below) and the new Credentials (IP address, remote URL, and auth) replace the existing credentials.
The node-address + SQL-Controller-Table-Base-Column-ID (as UDM supports multiple controllers) are the unique identifiers. The controller SQL-Controller-Table-Base-Column-ID is tied to the UUID however the UUID is not part of the Unique identifier. UD Mobile allows users to "clear" the UUID so the SQL-Controller-Table-Base-Column-ID remains intact when the UUID is cleared. UD Mobile will add the new UUID to the existing SQL-Controller-Table-Base-Column on Synchronization if the UUID is cleared.
At a higher level if the node-address does not change then customizations will remain intact. If synchronization prompts to "remove cached values" after replacing the UUID then create a backup before removing cached values. If customizations/favorites are removed restore the backup then adjust any customizations which were removed to point to the new node-address before synchronization again.
Insteon should be safe in most situations, other protocols/node-servers have enumerated node-addresses so they are susceptible to Address change. So keep node servers in the same slot and add all required parameters prior to synchronizing UDM.
https://wiki.universal-devices.com/index.php?title=UD_Mobile#Migration