Maxis has published The Sims 4 for Mac, with cross-buy for PC users.
This means whether you buy the game on Mac or PC, you can get a code for the other version. Note that the Mac version is a digital only release.
If you already bought the PC version, regardless if it’s digital or disc, all you need to do is log on to your Origin account from your Mac and you will be able to redeem the game immediately.
Origin can’t facilitate cloud save for this game, but you can just copy your save files from PC to Mac.
You can get more details from the official The Sims 4 page for Mac here.