The Xbox Series S is rumoured to include 7.5GB of ram (compared to the Xbox Series X 13.5GB of usable RAM), an underclocked CPU speed and around 4 teraflops of GPU performance (compared to the Xbox Series X 12 teraflops of GPU performance). The Xbox One X has 12GB of RAM and 6 teraflops.
Microsoft still hasn’t announced the Xbox Series S, but it’s been confirmed in developer tools, a controller box and an Xbox Game Pass pamphlet.