The Ars Technica review is thorough, and acts as a good set of "release notes", but it's published upon release, and obviously doesn't cover the stuff that devs and users discover throughout the following year.

I recommend the excellent EclecticLight blog (by H. Oakley). He doesn't try to do a comprehensive overview (you have Ars for that), but has done many technical deep-dives covering changes that haven't been talked about anywhere else, and I can't praise him enough for that.

Michael Tsai also has a great blog (mjtsai.com/blog/) that functions as a news agregator for Apple stories and commentary, and though his blog's not dedicated to only macOS, you'll find regular stories on technical details there.