I have this exact same configuration, with a domain just used for emails, and I can work normally with it.
But the domain is configured normally, and is not in "inconsistent" state, it is enabled normally, but I only disable the "www" at DNS configuration.
This is the only change I made.
The control panel is accessed normally too, in the customer panel.
With backups, I do it manually with a custom remote backup script.
Regards,
Netino