The biggest bummer of these machines is apples lack of vp9 hardware decoding in macos, it makes 4k youtube unwatchable. For high motion content (mountain biking videos) 4k is the only way to watch even on a tiny laptop screen due to youtube’s horrific compression. Its an absurd limitation considering the hardware has full support for it! I know it sounds insane but I returned mine for a quad core 13” mbp just to brute force software decode playback of these videos.
I wouldn't say it's the only reason. H264/5 are not royalty-free codecs. YouTube is a powerful tool Google can use to push a royalty-free codec, much like Apple used the iPhone to push people off Flash. It's one of few areas I agree with Google being heavy handed.
Does anyone know of a similar Safari extension? Battery life remains a concern, and switching from vp9 to x264 is great, but then having to deploy Chrome instead feels like a 1 step forward, 2 steps backwards situation.