Just for fun I downloaded this HDRI from HDRI Haven as it contains a “real” fire.
Tuning down the Exposure to -4.0 I get this:
Standard
Filmic
AgX
Tuning down Exposure to -8.0 this:
Standard
Filmic
AgX
The whole HDRI at Exposure 0 (left is Filmic, right AgX):
And now at Exposure 4:
Eeek!