The best system splits your valuables so no single mishap can strand you. Passports generally live best in the hotel or apartment safe, with a paper photocopy and a phone photo carried instead; most countries accept a copy for casual ID, though a few require the original on your person, worth checking locally. When you must carry the real document, an inner zipped pocket or a slim under-clothing pouch beats any bag.
Money belts still work for transit days, border crossings and long train rides, though wearing one for daily sightseeing is overkill in most places. The smarter daily setup: a modest amount of cash in a front pocket for the day's spending, one card kept separately from that cash, and the backup card plus emergency cash locked in your accommodation. That way a pickpocket or a lost wallet costs you a bad afternoon, not the trip.
A few refinements from long practice: keep small notes accessible so you never flash a full wallet at a market stall, use hotel safes but also a locked bag inside budget rooms without them, store digital copies of documents in encrypted cloud storage you can reach from any device, and note your bank's card-blocking process before you need it at midnight.