You say you're using the most current Mac OS? Would that be the one called, "Sierra"? If so, you're hosed, bud! AE doesn't run on it properly!
If I were you, I'd go back to the Apple store and DEMAND that they install Yosemite. Or El Capitan. Or whatever the last one was.
Would the OS really be the core issue? I feel like it's been a combination of the updates to CC and the OS' the Apple have been launching. Maybe it's time to go back to Windows?
Ae is buggy in Sierra right now and I would not expect for a bug fix update to be happening soon. I am running 13.8.1 on Windows 7 and the performance is much better than 13.7.1. I know some Mac users have had problems with previewing. especially with 4Kor 5K monitors. still you should specify your entire technical info so we can see what else can be done: FAQ: What information should I provide when asking a question on this forum?
I had a miserable time trying to run After Effects in Sierra as well but it has nothing to do with your laptop - I installed it on my desktop.
I contacted Apple to see if there was anyway to go back without a TimeMachine backup from when I was running El Capitan and they said there wasn't.
However, I found this link with instructions on how to go back to running El Capitan (I asked Apple and they said it may work but they cannot verify it):
I followed the steps but ran into issues in two places and was able to resolve them and reinstall my El Capitan.
Step 2: Creating a bootable drive
Enter the text below into the terminal instead of the Sierra path
sudo /Applications/Install\ OS\ X\ El\ Capitan.app/Contents/Resources/createinstallmedia --volume /Volumes/Untitled --applicationpath /Applications/Install\ OS\ X\ El\ Capitan.app --nointeraction
Step 4: Reinstall El Capitan
When attempting to reinstall El Capitan after deleting the only option I had when trying to reinstall OS was Sierra.
In order to see the bootable drive you created you need to:
- Restarted your computer
- Hold down the 'option' key when your hear the startup sound until your system loads
- Select your bootable drive and you'll be prompted to select where to save it to
- Select your Hard Drive
Make sure you have everything saved!
All your presets and plugins - EVERYTHING
You will have to install all of your apps, setup all of your system preferences - everything stored on your hard drive WILL BE GONE and you will need to restore it from your external and cloud drives. (I lost my VC Designer Sound FX and MotionPulse so proceed with caution!)