Shield Effect Power is fixed at [##]%
Your Shield Effect Power modifiers instead affect your Shield Effect Radius
[alt 2nd line: "Shield Effect Radius is increased based on your Effect Power modifiers"]
Dev & playtesters know best what to set the power to, and whether to apply the modifiers additively or multiplicatively. I first imagined 50% just to be cruel ahaha. Then again, if the second line was "Radius Effect Radius +(n-##)% where n is your Shield Effect Power modifier", it would be more exaggerated than cruel, but not as elegantly simple.
First draft was recursive mod where radius increased, but power gradually faded from centre (like Dying Star damage). Seems too cumbersome though - both computing-wise and to play with.
Come to think of it, an inverse where the power is strongest at the extremity and weak/absent in the centre is beautifully janky and forces you to use that big effect radius...
But the two liner description at the top of this post is still most elegant