Technique

In this texture, the red channel drives the shapes of the fire particles, using the sub UV feature of Niagara to randomize which of the 4 primary shapes it will use.

The age of the particle drives color, opacity and size, note how it goes from a magenta, to yellow, to red, as well as a general red glow flicker surrounding the system.

The green channel drives the shape of the smoke, with much of the similar features of the flame body, with a bit more consideration for how the particles merge into each other, in order to not make it too obvious that theyre just picking from 4 primary shapes.

The blue channel handles distortion for everything, I use a material function to avoid having logic duplicates, and that way if I want to change the logic of the distortion effect, I simply need to adjust that one function.

Finally I add a bit of polish by adding sparks with an aggressive curl noise.

Fire VFX in one texture.