AutumnLeaves4444 Having dual-channel RAM is a lot more important for some activities than others. Gaming is one of those where it's difficult to predict the outcome—it probably depends in large part on the game in question. So why not try it out and see what happens?
You could also add another 8 GB module instead of a 16 GB stick if it makes a difference. With that configuration, only 8 GB of the current 16 GB module would run in dual-channel mode, but that plus the other 8 GB would be more than enough to cover Sims 4. Additionally, RAM generally comes with a lifetime warranty because it's relatively simple to make at a high quality, so you could buy something used and probably be completely fine.