In terms of what settings is safe to play around with, playing around with Internal Resolution in Graphics > Enhancements is generally safe. If you have a 1080p display, set it to 3x.
If you're on the latest development build, setting shader compilation to "Async (Ubershaders)" in Graphics > General and check "compile shaders before starting" will remove shader compilation stutter during gameplay
If you're on the latest development build, setting shader compilation to "Async (Ubershaders)" in Graphics > General and check "compile shaders before starting" will remove shader compilation stutter during gameplay