Nice article. I didn't know about many of these.
I'm glad we can use logical properties now. Dealing with systems that support both LTR (like English) and RTL (like Hebrew and Arabic) languages used to be a pain because we had to have a build script that generated a second CSS bundle with everything flipped (eg converts margin-left to margin-right, border-left to border-right, etc. Logical properties make it a lot easier.
I love the gap property for flexbox... I use that one all the time. Easily solves the "I need padding between all these items, but no padding at the start or end" use case.