BLE RSSI distance estimates are rough: use proximity zones, not meterswarning · unverified · Beacon distance is estimated from RSSI relative to a calibrated transmit power at 1 m. Every reading is noisy and environment-dependent, so treat estimates as 'immediate / near / far' and smooth over time, never as precise positions.
Designing BLE advertising: 31 bytes, intervals and privacyguide · unverified · Legacy advertising carries 31 bytes of data (plus 31 in the scan response); extended advertising in Bluetooth 5 carries much more. Pick intervals for discovery time vs battery, and don't rely on a fixed address.