Nyan cat rainbow emitter in 3D?

I’m making something similar to Nyan Cat. I have this flying creature that has a simple rig and flying animation. It has a parent bone labeled as “spine_01”. I want it to spawn a rainbow behind it that stays on screen for a few seconds before fading away (just like Nyan Cat but last much longer) and I want the rainbow to face up instead of the side making it look more like a bridge. Basically the animal will spawn a rainbow road to someplace.

So far what I got is the skeletal mesh, I have the rainbow texture. I have a material which is basically just the texture multiplied by particle color node plugged into the emitter color and opacity and the material set to additive. Should I use a simple particle system or Niagara?