What you are describing is still basically a system of particles. Particles are not necessarily fuzzy-looking; if you want you could use them to draw an animated sprite from a sprite sheet without any translucency, even using the default (and legacy) particle emitters/renderers and no scripts.

Personally I've found that on some mobile devices, dynamic geometry can be pretty slow in Unity (which makes dynamic batching and Unity's built-in particle renderers and most sprite frameworks too slow), at least as of Unity 3.5. And moving and rotating and (especially) scaling many separate game objects with meshes attached is even more expensive on mobile.

So far, the most efficient alternative I've found is actually to call Graphics.DrawMeshNow with a 4-vertex plane mesh once per particle (where each particle is simply a Vector3 and/or a matrix that I update in a loop) inside the OnRenderObject of a game object. It sounds like it should be slower, but it avoids a lot of the CPU overhead that's usually part of Unity's rendering pipeline, and it gives you full control over the particles. But it's kind of advanced stuff to get it right, and regular particle systems are fast enough for many situations even on mobile as long as you take care to minimize the particle count and overdraw (which btw should be done either way).

Right, particles only have a "fuzzy cotton candy look" if you make them that way.