Is Update frames tied to gameplay FPS?

I do not want to lock my games' FPS. There's the horror stories of games where if you increase FPS above the 'limit' you speed certain things up and/or screw over the physics.

Is there anything else that I should be aware of in regards to preventing this?

 

http://docs.unity3d.com/Manual/ExecutionOrder.html

Update() is every frame.
FixedUpdate() is for physics. Framerate independent.

 

To unlock your framerate, make sure you set "Application.targetFrameRate" to -1. Once you do, make sure that whenever you have an update function, you take into account how much time has passed using "Time.deltaTime". So if you were moving an object you would do something like: "transform.position = transform.position + dir * speed * Time.deltaTime".

The reason games typically have locked fps is because it can be hard to have complex simulations work with drastically different update times. Unity's physics is an example of this and the way they solve it is that Physics updates at fixed time intervals. If you have something that updates and interacts with physics, you can use the "FixedUpdate" function however this function may run many times a frame or no times at all based on how much time has gone by.