Apple Notes is the default for a reason: it is free, fast, already installed, and better every year. An Apple Notes alternative earns its place by doing one of the things Notes cannot: run on Windows or Android, lock the whole app, encrypt every note, keep out of iCloud, or store notes as files you can open anywhere.
The six apps below each do at least one. We build Dash, so it is listed first and judged by the same rules as the others.