Do I have any control over a users and organizations ID? When migrating, I would like to keep the IDs that I already have. The same for devices which are service users. I would like to migrate the ID which may be a mac addresss

Ory assigns own unique ids to identities, but you can easily store your legacy id on an additional schema field.

You can also add it as admin metadata if it should remain internal to your system https://www.ory.sh/docs/kratos/manage-identities/managing-users-identities-metadata