I took the bold step to update the operating system of my mac to Mojave not knowing if Endnote will work or not.
So far I did not see any new problems wtih running X9 on MacOS 10.14. I tested a Word document with over 150 in-text citations and the CWYW plugin seemed ok.
When openeing X9 the first time you get a notification message that this version of EndNote is not supported by the operating system. You can click OK and hope that EndNote will release an update before Apple stops supporting 32-bit apps.