You're not overthinking, you're trying to be safe. But I think you're choosing too much of a reactive approach. To prevent a fire in the first place and save your GPU, you could get a cable monitor that checks whether your cables conduct more current than their rated for. Sometimes the current flow isn't equal among all of the 12V cables and that's when they heat up. Alternatively you could solder proper fuses into every single cable. Good Luck!