Two campfires, made in UE4, using particle system.
The stylised flames are inspired by the 'Stylized VFX in RiME' conference, that you can find on youtube. The fading smoke is obtained by substrating some noise on the texture and floor the result.
The "realistic" fire is simplier. I just animated the texture in a shader using distortions. Then, I use the shader for my particles. Using a dynamic parameter, I can play with the flames density, brigtness and offset directly in the particle system.