First off, if you do not know what rendering scale is, it basically renders the game world at a lower resolution than the monitors actual resolution, meaning that if you set your render scale to 50% and your computer runs on 1080p resolution than the program will only display 540p. It highly affects the graphics of a game. For example, if you play a game while it’s rendering scale is set on 50% it will display most scenery and character models as blurry and pixelated. But if you play with the rendering scale set at 100% it will be like playing a completely new game.
In terms of video games rendering scale sets the 3D scenery to suit your monitor’s default settings without having you make any adjustments yourself. In online games, it is more suitable if you keep the rendering scale at its default setting as it highly affects important things such as the displayed text, your crosshairs, the game’s menus, and other minor details.
The text, crosshairs, and menus aren’t affected by the GPU unlike the 3D scenery and solely rely on the rendering scale and its settings which is why it’s more suitable to run the game on its default rendering settings. Lowering the rendering scale will just tamper with the text, menus, and crosshairs.
Note that lower resolution is very noticeable on text, lines and simple drawn shapes that make up a significant part of the HUD and menus. In contrast, rendered 3D scenes are usually less sensitive to downscaling when it comes to perceived quality. A very low rendering scale will make the edges of rendered objects noticeably thick this is why you should not go below 75% or AUTO/66%. Instead of setting your rendering scale below this, it’s a better idea to lower some other settings if absolutely necessary.
Overwatch Render Scale
In Overwatch, a suitable resolution setting is very important as every minor detail is very important. Even the lines left behind by passing bullets are important as they can tell you where your enemies are firing at you from. Lower rendering scale might give you higher frame rates, for example, if you put your rendering scale on 70% you might get twice the frames per second than you usually do. This may sound tempting but it has huge effects on online gameplay and especially in a game like Overwatch.
The low resolution also tampers with some lines and most of the shapes present on the screen making sniping or simply attacking from a distance with characters like Ana, Widowmaker, McCree etc. near impossible. Playing a non-hitscan or better known as a projectile character like Hanzo or Pharah is actually impossible with an unsuitable rendering scale setting because of his style of play.
If you do not know what the difference between a hitscan and projectile character is, a short way to define both would be that hitscan characters are the characters whose shots land where the cursor is set, immediately after the shot is fired, whereas a projectile character like Hanzo requires extreme precision to play as their shots travel slower and do not land immediately, taking their fair share of time before finally reaching the target and Hanzo’s arrows also go lower than intended if they are fired from an unsuitable range.
So for the reasons given above it is advised that you do not tamper with the rendering scale settings especially in Overwatch as the added frames per second are really not worth it and will only worsen the way the game plays and feels