[@Charlie] This is something that is uncertain right now. Google is changing how they allow access to Google Drive’s API. If Google goes through with the changes, then Replicaro will be updated with the new directions on how to connect to Google Drive (you will need to create your own free client_id).
For now, just use Replicaro as normal. You will be able to easily switch to your own client_id without affecting your backups if Google makes the switch in the future. The client_id has nothing to do with your backups; it has to do with how the backups are accessed.