What would be an example of decoding-intensive video?
You could try to play 1080p and 2160p videos, possibly 60fps in YouTube. If you right-click on the playback window and click on "Stats for nerds" you will get more information about used video and audio codecs and dropped frames, which can indicate that your hardware may be too slow. Currently the videos are mostly encoded as VP9 codec, but you can change settings to prefer AV1 codec, at https://www.youtube.com/account_playback. However please note that not all videos are available as AV1, but you can find some videos at AV1 Beta Launch Playlist.