Hero4s do 1080p HD, right? Which can tax many lower power machines. Try setting it to lower resolution, like 720p
Are you saying you have a lot of lag and choppy after the render?
I have a 2.3 Ghz Intel i7 with 8GB RAM and intel HD graphics 4000 that has no issue, except for one need to be patient.
What apps are you using?
The issue is playback, either directly from the camera/SD card, or after import to Photo or iMovie. I use iMovie almost exclusively for editing, although I'm less of a fan of the newest version so far.
I have been filming and editing in 1080 for years without an issue. I am using two new cameras. I have filmed in 1080/60fps on the H4 Black, and 1080/30fps on the H4 Session. 1080/30fps is exactly what I was filming at with my previous GoPro. The file sizes are slightly larger for a similar length clip on the Session, but not dramatically so.