Re: sims 4 lagging on mac
Follow these steps to launch a new clean game and see if it still lags with a brand new save. Do not copy any of the contents of your current Sims 4 folder to the newly created one yet - https://answers.ea.com/t5/Technical-Issues-Mac/READ-FIRST-Sims-4-Mac-Help-Guides-and-Troubleshooting/m-p/4612394#M163
How much storage is available on your Mac? About This Mac > Storage.
Check the bug forum too. If your lag isn't caused by ageing hardware (possible) it may be the usual simulation lag that is often reported and an ongoing issue https://answers.ea.com/t5/Bug-Reports/bd-p/The-Sims-4-Bugs