Decision rule
Using the device passcode is usually simpler across current Apple devices. A custom Notes password creates separation, but forgetting it can permanently block access to notes locked with it. Resetting a forgotten custom password does not unlock older notes.
Compare before choosing
Device passcodeLower memory burden and works with Face ID or Touch ID where supported.
Custom passwordSeparate secret, but it needs an authorized recovery record and careful handling.
BiometricsConvenient authentication, not a substitute for knowing the underlying passcode or password.
Multiple accountsLock settings can differ by Notes account; verify which account holds each note.
Test before migrating
Lock and reopen one non-sensitive note on every device you rely on. Do not move the only copy of critical information until access and backup plans are confirmed.
