Depends...
Hopefully you understand that real-time video encoding is VERY computationally demanding. So it depends on how old, as to whether a given system would be up to the task. And then there is Operating System (OS) compatibility. And then there is optimizing both OS and OBS for an under-powered (possibly) system.
I recommend monitoring hardware resource (CPU, GPU, RAM, Disk I/O, etc) utilization [for Windows OS it would be using Task Manager’s Performance tab and/or Resource Monitor] to see if your system is being maxed out with your settings. You'd need to look up whatever teh MacOS equivalent is.
It would be helpful is you indicate which model Mac, and its CPU, GPU, Disk, and RAM, and what you plan to do on that system (gaming, vs maybe just a webcam, mic, and a music sheet or other simple display (powerpoint, etc)..
