TL;DR
Still under embargo from the US government, Huawei is prohibited from integrating Google's latest proprietary technologies, including Google Play Services and apps like YouTube, Gmail, Google Maps and many others. Perhaps for this reason, EMUI 12's list of changes is a bit more discreet than previous versions.
Still, the system is still under development internally and Huawei has already announced the list of 28 phones that will receive the customization update.
Preliminary information indicates that the skin runs on top of Android 11, and is equivalent to the HarmonyOS 2 system. EMUI 12 brings a new look to interface similar to Huawei's "own" operating system, with a new Control Panel, with quick access to the devices of the manufacturer's ecosystem.
Other changes highlighted by Huawei - both in EMUI 12 and HarmonyOS 2 - are the minimalist interface, with a strong influence of neumorphism, animations and more natural animations, "which imitate the look and feel of the HarmonyOS 2.s, more natural animations, "which mimic how celestial objects move in the universe", and the HarmonyOS Sans font, with the option to adjust size and weight.
And not to be missed, EMUI 12 brings even greater integration with Huawei's other devices, the MatePad button on the Control Panel, for example, allows you to make calls, check photos and messages from your phone on the tablet screen. The MateBook button promises to simplify file sharing, while the Vision and headset buttons enable content playback on connected screens and headsets.
According to Huawei, the update to EMUI 12 will begin rolling out to announced devices in the first half of 2022.