For either user data security or legal liability, Google Drive account that is protected by two-factor authentication and a strong password is fairly secure.
We can tell from the process that files are uploaded to Google Drive:
1. Before your files leave your devices, it is encrypted using TLS standard by Google, whose security is as strong as your browser connections.
2. After your data is uploaded to Google Drive, it gets re-encrypted using 128-bit AES, which prevents the possible leakage of unencrypted data on their hard drives.
3. The AES encryption key would be encrypted with a rotating set of master keys again.
4. When you retrieve your file from Google Drive, the process is simply reversed and as safe as how it gets uploaded.
You can learn more to help you decide in this article: Is it Safe to Store Sensitive Data like Passwords on Google Drive?