Storing secret key (emergency kit)

Someone from 1Password will surely add to what I'm about to say (and please do correct me if I'm wrong), but my understanding is that the purpose of the Secret Key is to protect your data in case 1Password's servers ("cloud") were to be hacked. The Secret Key provides a guarantee that no matter the strength of your Account Password (nee Master Password), the data stored on 1Password's servers is at least encrypted with a 128-bit key, i.e. the Secret Key.

Because your data is encrypted with your Account Password in addition to the Secret Key, it's perfectly fine to store the Secret Key somewhere else, be it locally or on some other cloud server, as long as it is always accessible to you even if you can't log into 1Password, because you'll need it in order to log into 1Password on a new device.

If you use the mobile app, 1Password in fact already stores your Secret Key in the cloud as a security precaution, because if you reset your mobile device and log into your iCloud or Google account and then proceed to install the 1Password app, you'll see that your Secret Key is pre-filled for you, and you'll only need to provide your Account Password. This implies you know the password to your cloud account, of course.

Still, I'd recommend haivng a physical copy of the Secret Key stored somewhere safe like a safety deposit box or a trusted family member or friend, just in case.