Important papers like passports, birth certs marriage certs divorce papers, insurance documents or paperwork that you could not be without in the event of a calamity, I wouldn’t be looking for a box file, but rather a fireproof box.
once I had tat, I’d place everything in there that I felt need to be protected, and put a couple of silica bags in too, to stop any damp damage.
I really hope this helps.
if possible, and if you need it, try to find a fireproof box that has keys.
if you want the box to also hold anything valuable, I would try to find a way to secure it in the event of (even if you think it’s unlikely) a burglary.
Eg screw base of box into say the bottom of a wardrobe or floorboards etc.
Precious papers can’t alway be replaced, and those that can might probably be costly to replace.