Unfortunately, the correct answer is.... it depends
As the whole point of OBS Studio is real-time video compositing (combining multiple sources), the question becomes what all else is running at the same time.
Then, MacOS users are not known for doing basic resource management (under silly notion they don't have to). So, there are plenty of MacOS users that leave lots running in the background. If that is you, then you may need more RAM. if that isn't you, it still depends on overall system utilization
Then, there are things like using Studio Mode (Preview Window) that takes 2X rendering, and extra RAM. Or things like chromakeying. System requirements can vary greatly.
And a thin 'n light (air or pro) Mac laptop/notebook is subject to thermal throttling, so you will need to temper your expectations vs a much more performant desktop computer. Now, don't get me wrong. The Air or Pro could be just fine for you. or not. Without you having a much better understanding of your requirements, it isn't possible to provide a good answer.
