I cannot answer with a technical comparison of the various formats because I have no technical knowledge of them, only some practical experience.
Afaik, all distributors (and publishers) other than Amazon itself, that make ebooks available for the kindle, use the MOBI format. That includes TOR, Smashwords, Arc Manor (Phoenix Pick), Humble-Bundle, Story-Bundle, Wildside Press (and Blackcat), Book Funnel, ... and I am forgetting several others (I buy mostly SFF books, so that restrict my exploration of the market).
Actually after 5 year of looking for ebooks sources, I know only Amazon as a distributor of azw3 (or other letter-digit combinations). And my experience with Amazon is only an endless struggle with format decoding problems. But there seems to be one constant : the kindle does accept the MOBI format.
According to the article you reference, it will continue to do so: "Amazon will still be delivering MOBI files to Kindles". They say nothing about other Amazon formats.
You remark that Amazon doesn't support anymore MOBI for upload on their platform; That is mostly true, but only because they switch upload to EPUB. Afaik, their other formats were never used by authors to upload books. They wre only for download.
My opinion is that sticking to EPUB and MOBI is the safe choice. Actually it may be the only technically available choice. Since everyone, other than
Amazon, is using MOBI for the kindle, there is probably no market for software
that would give other options.