To adjust video quality, go to Start > Settings > Gaming > Captures > Recorded Video.
Under Video frame rate, choose between 30 frames per second (fps) and 60 fps. Video quality controls both fps and bit rate or megabits per second (mbps).
Game clips are recorded at the video resolution specified in the game, up to 1080p. For games played at a higher resolution, game clips will be scaled down to the selected level. Higher quality and resolution generally requires the PC to work harder, which may decrease performance. Try them out to determine the best settings for your system.