I find the overview videos really useful for focusing on the big things, but only you know which parts are important to your institution, so trawling through the release notes is the thing to do. I do this every year for our team - it's time consuming - but necessary.
Check out the videos at: https://www.youtube.com/c/moodle/videos
Check out the videos at: https://www.youtube.com/c/moodle/videos