These features have not landed in any stable browsers at the time of writing. However, everything discussed is already in Firefox Nightly by default and key parts are in Chrome Canary (with the Experimental Web Platform Features flag enabled), so I recommend using one of those browsers (when reading this article) to see as many of the features in action as possible.
Regardless your preferred method of animation on the web, there will be times that you need to animate the same property in separate animations. Maybe you have a hover effect that scales an image and a click event that triggers a translate — both affecting the
transform. By default, those animations do not know anything about the other, and only one will visually be applied (since they are affecting the same CSS property and the other value will be overridden).