You can use youtube-dl (a wonderful command line utility available eg on home-brew) to easily download the videos at your desired quality and and watch from your HD whenever/however you like.
People often assume that youtube-dl only works with YouTube because of the name, but it actually works with a really huge amount of sites, including Vimeo and Twitch.
You can see the full list of extractors that they have in the source here:
Perhaps they should just rename it to something more generic like "video-dl", but then again I suspect its primary use is for YouTube and the other sites are just "extras" it grew over time.
https://youtube-dl.org