I've read in multiple places that hybrids are the worst, then gas, then BEV's (EV's based only on battery, not hybrid). That is, in terms of frequency of fires, not how hard they are to put out.
But to be honest, I'd like to look at the raw data. For example, I don't know if the gas car fires are more frequent than EV's only because there are still some decades old gas cars on the road. I'd prefer to see comparisons with same ages of cars.
“When and how often, by comparison, do gasoline or diesel cars go up in flames on there own?”
How often do ICE fires spontaneously ignite and sink large cargo ships? Two spontaneous EV fires doing exactly that in less than a year.