Avid released a statement today recommending that Pro Tools users on Mac DO NOT update to macOS 10.14 Mojave yet.
Here is the alert from Avid:
Initial testing of Pro Tools with macOS 10.14 has shown serious problems with CPU performance at lower buffer sizes. Avid is working to find a resolution for this problem. It is recommended that users refrain from updating to 10.14 until further notice. If you have to use 10.14 then make sure to avoid lower buffer sizes (64 samples or lower at 48kHz, 128 samples or lower at 96kHz, 256 samples at 192kHz)
Check this page for the latest Pro Tools System Requirements.