You can change how much you want to downscale in Settings > Video > Output (Scaled) Resolution. So you can downscale your resolution to 720p (or lower) to keep your image the same, but using a smaller resolution to reduce CPU load. You may want your base resolution at 1080p, since that's the resolution your content is in, but your CPU may not be able to encode an un-downscaled 1080p video. When you downscale, OBS takes your scene and shrinks it as much as you tell it to before giving it to the encoder. The most common way to reduce CPU usage is to downscale your resolution.

For example, 1080p has more than twice the number of pixels in each frame versus 720p, and your CPU usage increases accordingly. The resolution that you are encoding at has the biggest impact on CPU usage. Here are some ways you can reduce resource utilization and, hopefully, make both OBS and your programs run faster while encoding: In some cases, OBS will say 'Encoding overloaded!' on its status bar, meaning that your computer can't encode your video fast enough to maintain the settings you have it set to, which will cause video to freeze after a few seconds, or periodic stuttering. However, some people might experience high CPU utilization, and other programs running on your computer might experience degraded performance while OBS is active if your settings are too high for your computer's hardware. OBS uses the best open source video encoding library available, x264, to encode video. Encoding video is a very CPU-intensive operation, and OBS is no exception.

Best output settings for streamlabs obs