Hi Josh Oyen Beats,
Sorry for this issue. Did you ever find a solution? Please let us know if you have or if you still need help.
I resolved my playback issue with Adobe After Effects CC 2017 preview. Payback was really slow (and not in real time) - even though I have a souped up computer with plenty of RAM, hard drive space, and computing power. I resolved the issue by stepping down the resolution (in a box below the preview section) until it began playing in real time (half). It does not look as nice, but it shows all of the effects in real time - which is ok with me for a preview.
A workaround before I figured this out was rending the file to avi. It played back to the screen properly in real time while rendering the file. So, as least I could see what I was working with.
No fiddling around with a bunch of setting. Just a quick adjustment and the preview works like a preview should.