Since acquiring the Discovery Vanity shield, I'm curious as to some of the graphical effects.
First, it makes the impulse and warp trails white. I don't see any reason why the impulse trails are changed, since Discovery's are red. And while I realize it's TOS era, Discovery's nacelles have blue energy, so I believe the warp trails should be blue.
Next, at full impulse, a green trail appears out of nowhere, and overlays on the white.
And finally, using another engine with a graphical effect just overlays it rather than overriding it altogether.