thank you for your answer
The built-in Notes app works very well and syncs across Mac OS and IOS devices.
I use Notebooks App: https://www.notebooksapp.com
There are versions for Mac, Windows and iOS. A new Mac version is due soon.
For me it’s Bear from http://www.bear-writer.com. What a nice tagging feature they embedded.
DevonThink to go is pretty cool. Lots of features, markdown support, iCloud or Dropbox, encryption and OmniFocus integration. https://www.devontechnologies.com/products/devonthink/devonthink-to-go.html