I’ve just tried this briefly, but it seems to work & I didn’t see it mentioned here. Normally, the MacOS app for OP-Z is a CPU hog and added a new droning fan track to the mix, but this trick seems to about halve the CPU load on my 2015 13" mbp:
- in Finder, open Applications, find the OP-Z app
- right click the OP-Z app icon and click “Get Info”
- under General, click the box for “Open in Low Resolution”
- restart the app if necessary
I’m completely new, so please forgive me if this was already common knowledge.