Check Preferences/Memory and Performance and make sure that an even multiple of 4 GB is assigned to other apps. You'll want 4, 8, 16, not 3, 6, or 9. Modern computers like multiples of 4 are much better than any other value.
While you are in Preferences, also check the Media and Disk Cache panel and make sure that you have not assigned too much storage space to the Disk Cache. I keep mine between 20 and 40 because it takes a long time to empty any more than 40, and that's plenty for most comps.
Also, check the Project Settings (Shift + Ald/Option + Ctrl/Cmnd + K) and try changing the video rendering and effects options in the first tab.
If you use an external drive for Disk Cache, ensure that the cable is high quality and that the transfer speeds are acceptable. A cheap USBC cable can be 10 to 15 times slower than a high-quality Thunderbolt cable.
You also want to ensure adequate drive space on your boot drive. It is also a good idea to close other apps you do not need.
I hope these suggestions help. If you can't fix it, try rolling back one version using the Creative Cloud app. Let us know if you can't figure out how to do that.
While Rick's right on all his points, I picked up a little on your use of words like "editing" and "playback". After Effects is not a video editor. Premiere Pro uses the original files to playback edits, whereas After Effects builds each frame into its RAM. That green line in your screenshot is the amount of frames AE has ready to playback, the rest will be played line (no line) or retrieved from temp files (blue line).
To build up the whole sequence, hit 0 on your numberpad, let AE assemble as much as it can, then it will loop. To hear any audio, AE is done with silent preview, hit the spacebar to watch it all back together.