How do I set video recording rate to 60 fps or 120 fps and change between the two? How do I set video recording rate to 60 fps or 120 fps and change between the two? I'm looking to be able to use different FPS rates when recording video with the iPhone 5s.
the only option using the iphone's camera is by switching between Slow-Mo and Video modes. You can then speed up a Slow-Mo video to normal speed in the photos app pretty easily. You can't convert normal videos to Slow-Mo.

There are probably a ton of apps that offer a bit more manual configuration than that. But I don't know of them.