Actually, I've realized that it only lags when I put an effect on it. But all I did was reverse the footage, so nothing really taxing. Playback without any effects runs lag free at 1/4.
Heres a link to my build, https://pcpartpicker.com/user/Cbach246/saved/#view=4xTsYJ
All of the drone footage I've worked with has been H264 and therefore highly taxing to the computer system overall. If you're going to be doing a lot of editing of that footage perhaps the best approach is to transcode it to a better format for editing (i.e., pro res or dnxhd.)
Have you tried placing the footage in the SSD?
I believe the hard drive is the bottleneck here.
As I understand the best situation is having the footage on one SSD and the cache and projects on a separate one.
Since you have a nice build it's probably worth doing.