Is there anything more secure than a password protected SparseImage against state actors? If you had to secure important document in an encrypted, yet easily accessible format from state actors; would there be anything better than an password protected sparseimage? I used to use cryptkeeper in linux. A password protected sparseimage is the closest thing I have found on the mac side. Since this occurred (https://www.macrumors.com/2017/10/05/macos-high-sierra-disk-utility-vulnerability/) I am doubting that choice.
Encrypted disk images are secure. The issue that you referenced is a user interface bug in Disk Utility, not a problem with the encryption. You can also create disk images without using Disk Utility, e.g. using hdiutil on the command-line or a utility such as DropDMG.