UPDATE FIXED:
For anyone else who has this issue, here’s how I fixed it.
You DO need a decent USB cable; one that isn’t just for charging but also data transfer.
You do NOT need the SiLabs USB drivers for the MK2. My MacOS recognized the radio and named the dual ports “usbmodem147101” and “usbmodem147103”.
You DO need to change the default CI-V address to “94h” from the default of “B6h” in the MK2.
You may find the radio isn’t saving that change if it’s like mine. Once I got cat control working, I saved the settings as a preset in MENU/2/Preset for both data and SSB. I used the internal preset for FT8 as my base, changed the CI-V address and wrote it as a new preset. 
What’s the secret to getting cat control, or for that matter, just the USB drivers to show up on MacOS? Just bought the MK2, hooked it up and no matter what I do, I can’t get cat control. All internal settings in the radio are checked and triple checked correct. Tried 3 different cables. Installed the old SiLabs USB drivers like we had to do with the original 7300 and they either don’t work or (when uninstalling to reinstall) don’t show up at all sporadically. This radio is going back if I can’t get this resolved tonight. What a PITA. I appreciate any help.