Not so fast. On the B737s (-300 thru -900), the amount of loop sensing a fire has nothing to do with whether an overheat or fire warning is generated.
The fire loops have different alarm settings. As the resistance decreases in the kidde system used on the B737-3/4/500s, the first alarm setting will generate an overheat warning. As the resistance lowers further, the second alarm setting will generate a fire warning. The Systron Donner system used on the Next gens, though using the gas pressure method, still has the different alarm settings.
One loop sensing a fire or an ovht won't give any kind ogf warning until both sense it (during normal ops).
I will be honest, I can't say with the-200s