Earlier quoted context omitted.
The W3C version is a sporadically updated, bad-faith fork of the WHATWG version, created to maintain the fiction that it "owns" HTML, which it deems necessary to maintain the organisation's standing (and funding) in the eyes of other organisations and governments.
And yet, we don't get things like that changes page from the WHATWG version. (Unless you want to dig through the whole commit history) It's absolutely a fiction, but at the same time, this at least attempts to be a standard. The WHATWG version seems more like a reflection of "oh by the way that's the rules our browsers are following this month. Your's truly, the browser vendors."
So far we've done our best to keep a really readable, tidy Git commit log, which should help with understanding changes: https://github.com/whatwg/html/commits/master
If you omit the "Editorial:" or "Meta:" commits, I think it's actually at a similar level of detail as the W3C fork's changes log. (Not completely; scrolling through I do see a number of commits that wouldn't be relevant.) But the W3C fork has only managed to copy-and-paste a small subset of our changes, so indeed, the changes log for the last year of work at the WHATWG will be somewhat daunting compared to the small subset they managed to copy over.
There may be room for someone to compile a higher-level "this week/month/year in the HTML Standard" or similar; before I started working in the WHATWG, that actually used to exist: https://blog.whatwg.org/category/weekly-review (also in very amusing YouTube form: https://www.youtube.com/watch?v=1Bg5BPnmj68). So far we haven't had the bandwidth to restart that, but if you or someone else wants to contribute that sort of thing to the blog or elsewhere, I'd love to help you get started.