Hello Twwwt :)
You can use the middle charging pad as well as the left MagSafe charging pad for charging older non-MagSafe iPhones. I have two of these pads and use one of them at home to charge an iPhone Xr and an iPhone X respectively.
As with a "normal" Qi charging pad, you may have to search a bit for the optimal position. Furthermore, this charging pad will not wirelessly charge your iPhone at more than 7.5W. If you plan to use your Xs for a longer period of time, this product may not be worth it for you. However, if you are planning to upgrade your iPhone in the near future or if you own a Watch from Series 7 (Quickcharge), then this pad is an absolute recommendation ;)!
Alternatively, this product might be something for you:
Belkin Boost Charge 3-in-1 Charging Station (7.50 W)