Hello, I don’t know if you still have the issue but for the main question, there’s a parameter in the mutator device called “Enable VFX”, if you untick that you won’t get the blue FX spawning on entering it.
For your other questions, I guess you could also use a trigger to monitor, or even use a custom function that uses the fort_character.GetTransform() values, but the mutator looks fine to me.
If you wanna scale up your triggers I think it only goes up to 5, maybe you can attach one to a prop and scale this prop to make it bigger ? (didn’t test it though)