Thanks again for the answer !
I think you confirmed most of what I understood about trails, I’ll try to solution you gave me. For the stretched ribbon, I don’t think it will fix it thom the trail will still be dragged around. I was looking at this post Breakdown of ghost trail , there is some scrolling noise as you said, but the end of the trail is still moving with the head. It works great for this effect, but it can’t simulate smoke that stays in place once spawned.
For the mesh trail, it’s not what I meant, but still a good idea, thank you ! What I was talking about was basically how to achieve the ribbon effect (or trail renderer) : each square of the trail looking at the camera while still keeping the same curve. Twisting the trail if you want. I know it’s something like the cross product of the trail direction and the vector to the camera, just have to work on it. It could be useful for the effect in my other post.