I also have a 5S and i just installed beta 2. What i am seeing is the control centre has stuttering animation and also the multitasking screen. Do you also notice the same?
I noticed the same on my iPhone 5 after a full reset.
In terms of smoothness it is almost on par with iPhone 6. Not trolling. I did not experience stuttering animation when using CC. On multitasking screen yes a little haha.