TweenPosition is always fixed. It will go from point A to point B. With different resolutions and aspect ratios, the points may not be the same. On one screen target point can be at 300x200, on another screen it can be at 400x300, for example.
If you want it to be relative, then it's up to you to pass proper values to the TweenPosition script via TweenPosition.Begin.
TL;DR: Code.