For those experience lag when using a smartphone as the display, the following fixed the issue for me (at least with version 1.8, will let you know once I try with v1.9). On the PC running ACC and Simhub, open a tab in the browser and run Ensi Ferrum's dash, in the background.
Now, I've only been running Simhub (and this wonderful plugin) for a few days, so not sure why this would stop any lag issues. Maybe the PC is calling for the updates, rather than the smartphone. Anyway, hopefully this might help others who were having similar issues.