I use the xbox recorder since I play on a low-end laptop and it cannot show 2 windows at the same time unlike other recorders such as obs.

In portal 2 you dont need to record a video at all. If you chose to record demos you will get the same performance as if you were not recordding at all. It's slightly more hassle to submit, but very worth it if you cannot handle recoring.

Here is cant even's video explaining how to set it up: https://youtu.be/ZjQJmEPy50Y

Sonic Adventure 2: Battle

Portal 2