Proper Fixed Timestep for 30 FPS

Hello. I am having this issue, where my whole game jitters (Small fast jumps every few seconds). The game runs on iOS device with about 40 FPS, but i've decided to limit it to 30FPS with Application.targetFrameRate. The problem is that if i leave the fixed Timestep to 0.2 or 0.25 the game jitters all the time. It's pretty tiny jitterring and barely noticeable, but it's there. So i've decided to set the Fixed Timestep to 0.033333, which shoud be for 30 fps. Anyway, the game now runs super smooth, but these jitters occurs at some point, (Like every 4, 5 seconds). I am reading from 2 days, what's been discussed in the forums the jitter camera problem, from the LERP, but there's no clear answer on that. My player moves with FixedUpdate and the camera follows it with FixedUpdate... So my questions are: What is the proper Fixed Timestep for 30FPS? If the game can run with 40, 45FPS, shoud i limit it to 30, or leave it on it's own? What coud be causing the jitter if the game runs with good FPS? When i limit the game to 30FPS and when i monitor the FPS, its allmost perfectly staying on 30FPS (It goes from 29.94 to 30.05). So coud these variations cause the jitter every few seconds, if the Fixed Timestep is 0.033333 ? Any advice will be appreciated, to stop that jitterring... Thanks