I’ve started to experience quite high CPU usage when watching youtube videos on 1440p screen (video sample). By default, youtube loads videos in VP9 codec. Using this codec results in 80% CPU usage (i3-8100T). By installing this extension enhanced-h264ify and by blocking VP8, VP9 and AV1, youtube will load videos in avc1(h.264) codec. The CPU usage is down to about 30%.

Unfortunately, this will disable all 4k videos - they are available only in VP9.