Thank you for your post.
In our testing, we found that CS6 and the updated MAPublisher 10.4 seemed to work “okay” on MacOS 10.13 and 10.14. We did find that CS6 was producing a crash log when closing the software, but again, there was nothing obvious that we were seeing as being problematic with how the software was functioning. Unfortunately, I cannot speak to the Fusion drive and how that impacts the CS6 functionality.
Ultimately, the decision will be yours on how you want to proceed. Adobe no longer supports CS6 which is why the higher operating systems may not function 100% with it.
If there is anything further that we can help with, please don’t hesitate to reach out to us via help.avenza.com!