Running Activity Monitor while the system is idle, under normal use, and running After Effects may help to get an understanding if system resources are being taxed. Under normal use like editing documents, web browser use, etc then I'd not expect to see beachballs given the current system configuration.
Console app may also reveal if there are any app crashes or similar problems that could be contributing to the beachballs.
Running Apple Diagnostics is another option to see if there is anything wrong at the hardware level.
https://support.apple.com/kb/PH18765?locale=en_US
If your system is under warranty/Apple Care, then suggest asking Apple to run additional diagnostics to see if they can find out what's going on.