IN addition to what PaiSand said
realize there isn't a more specific answer to your question because ... it depends
How is your operating system setup ? Default or more optimized for performance (lots of silly defaults turned off/disabled, eye-candy turned off, etc)
Then there is what EXACT workload will be running in addition OBS Studio? Some workloads are very taxing others aren't...
Then, within OBS Studio, some settings will be more CPU intensive than others, but desirable nonetheless... but we can't know in advance you what your CPU load is, spare resources, with safe buffer room, etc.
And not all workloads (games, slide shows, pre-recorded media, etc) will work with the same capture/compositing settings