Just went through this. Sample size one:
While the fire resulted in the total loss of the house it was actually the water from the fire department not the heat that did proportionally more damage.
As a mental model you shouldn’t think of it as “what if my house burns down?” so much as “what if nice strangers roll up to my windows and chainsaw through my roof and spray 50,000 gallons of water in here?”
Yes everything in the mechanical room melted but everything in the rest of the house got hot, smoky, soaked and then moldy.
For root of trust materiel like social security cards, cash, passports put in a ziplock bag in a fireproof, waterproof safe. But for other storage I use clear “Ezy Storage” brand stackable 50L tubs labeled with Homebox QR codes. In the US, Target and Home Depot frequently stock them. I am very anti black and yellow tubs.
The majority of work post-fire goes to itemizing your house inventory for insurance. Even cataloging all your bathroom’s soaps by brand name rather than generic can make $100 difference. Multiply that by 500x different things.
From a threat model perspective I look at rooms from a “what would be salvageable in here if I emptied a swimming pool’s worth of water from some fire sprinklers”. Furniture and TVs are easy to replace. Other stuff less so.