I'm in the same boat, my so called Pro machine the USB-C 2017 MBP has had glitching out completely unusable rendering on the latest version of Illustrator since October 2017. Adobe blame Apple, presumably Apple blame Adobe because neither of them are fixing it.

As if my deteriorating keys on this machine were not bad enough. This wasn't a good WWDC for me. My PC is working great despite being an obscure setup with mismatched GPUs, can't say I understand why the graphic designer workhorse machine MBP is unusable with Illustrator and that is working just fine..