I don't think you can run the latest on an OS as old as 10.11. That said, be aware that there are significant issues trying to run on 10.14 or 10.15.
From my personal experience the current sweet spot for OBS on MacOS, especially on old Mac Pros, is High Sierra 10.13.
That said, you may be able to get it running just by deleting:
~/Library/Application Support/obs-studio
Back that folder up first if you need it, that's where profiles and scenes are stored.