Macbooks with a promotion display by default have "pro motion" turned on in the OSX settings app (go to Settings / Displays).
This is not conducive to smooth gameplay where ideally you want your 120hz (or higher) display locked at 120hz.
We recommend turning off Pro Motion and selecting a fixed refresh rate - preferably 120hz or higher.
Then in the simulator you can turn on v-sync in screen settings and the frame rate should lock nicely to 120 FPS (or whatever hz rate you selected.
The only downside here is early M1 Macbooks despite have 120hz displays only have 60hz as an option in the pro motion settings. Which of course is not ideal.