Re: Will I be able to transfer all my Sims 4 DLCs to Steam from Origin???
@lihhital You won't be able to use any of your Steam-owned content in macOS. So it's probably easiest to just create a new Origin account and buying whatever you'd like to play on your Mac. I mean, you could also buy codes for all the Sims 4 content you want elsewhere and register everything in Origin, but that could be more expensive than buying directly from Origin.
If this Mac has an Intel processor, you could instead partition the drive and install Windows on one side. This is known as Bootcamping, and the idea is that you boot into the OS you want to use and run it natively either way, with no performance hit from virtualization. A standalone Windows 10 license is probably cheaper than rebuying all your Sims 4 content anyway, especially if you find an older version on Amazon—since you only need the product key, you don't care if the install medium is from c. 2017. Bootcamp is not available on M1 Macs though.
Your saves and other user data can be transferred between installs, accounts, or computers, so all of that should be fine no matter what you do as long as you use the same packs for the saves. Trying to load a save without a pack present that the save formerly used could corrupt the save, or it might not load at all.
By the way, is there a reason you want to play on a Mac now? Depending on the hardware of the Mac and Windows PC in question, you might be better off, in terms of performance, just sticking with Windows.