Animation performance

Hi everyone, I’m planning to start my newest project in Unreal Engine and I am responsible for the animations. I had some issues with finding a good way to create character and UI animations which would be best for the performance on a mobile device.
Also wanted to include that I am new to the ue4. Is there something particulary important to pay attention to as a beginner?
Another question is if it’s better to use After Effects or animate with widgets in Unreal?