I've been playing SC2 since WOL beta and throughout the years I've mainly played on Windows. However, I'm an avid Mac user and would love to figure out some of the weird issues that keep plaguing me in SC2 on OSX Mojave 10.14.5 (most up to date as of 5/31/2019).
I'm on a MBP 13" TouchBar with a 3.1 ghz core i5, 8 gb ram, Iris Pro Graphics--more than well enough to run SC2 at medium resolution on low graphics, I don't usually experience any visual frame rate lag.
What I do experience is the equivalent of mouse lag, where my mouse (Razer DeathAdder) just doesn't seem to keep up with what I'm doing. I've read numerous places that this is due to Apple's inherent 'mouse accel' which I've tried to compensate for with Razer Synapse, SteelSeries ExactMouse and even SteerMouse. No matter what I do, my mouse just isn't coherent: it lags when moving across the screen, if I'm trying to drag a box to select units, it sometimes skips and I lose a drag, or it jumps me across the screen. The closest I can describe it, without recording it in someway, is when you see someone in a FPS with a bad refresh rate, they sorta skip across the screen oddly and their sprite has no smooth movements. I've also tried other mice and had similar effects.
I've spent hours googling solutions, paid for SteerMouse, and I still can't figure out how to make this work. I should note, this only affects me IN SC2--I can play CS:GO or some of the old COD games/other shooters without any mouse issues.