If you use Origin, you can easily move games from one drive to another from within the app. Just click the game in your library, click the settings icon, click "Move Game," then select a destination folder on your other drive and Origin will move the game for you and know where to look. I've found that The Sims 4's load times aren't terrible on my external hard drive (where I exiled it).
Some other ideas:
* If you happen to have a ton of files in your Screenshots or Recorded Videos folders (for either game), you could store those on a separate drive to free up some space.
* You can use Microsoft's Disk Cleanup tool to clear off other unnecessary files (like leftover installation files from Windows updates or leftover previous installations of Windows, if you're comfortable with that). Some of those folders can be up to 30+ GB large and are literally only sitting there in case you want to roll back to a previous version of Windows.
* Non-space related: if you play with all settings at max, bringing your Lot Detail down to 3 or 4 can help reduce lag even on very high-end PCs.