The recent Patch 1.58 not only added the PachiMarchi Challenge, but also some important enhancements for the Xbox Series S and X versions of Overwatch. Now players can decide if they prefer to play at a higher frame rate, or with an increased resolution.
There are three new different modes to select from. "Resolution" allows for "higher resolution outpost at the cost of image-quality". Xbox Series X users will play in 4K and 60 fps, while Series S players will get 1440p and 60 fps.
On the other hand, "Balanced" mode sacrifices resolution but allows for a higher-fidelity image. The game will displayed at 1440p on Xbox Series X and at 1080p on Series S.
If you only care about performance, "Framerate" is your mode. This will let both Series X and S users to play at 120fps, the former at 1440p and the latter at 1080p. It's worth mentioning that that you will need a TV that supports 120hz or VRR (variable refresh rate).
Any of these three options can be selected from the main menu, inside the graphic options and by choosing the "Preferred Mode" setting.