FSNotes is modern notes manager for macOS and iOS. This app respects open formats like GitHub Flavored Markdown, so you can easily write documents on iPhone and MacBook.
I LOVE the fill direct markdown output, so ZERO lockin to it if you want to leave. I also love that it uses iCloud to sync along with gist intergrations. I set a symlink from the iCloud folder to my dropbox so nothing is ever gonna get lost. I had an issue with notes from Apple where I lost a few things. I have been using SimpleNotes, StandardNotes and Evernnote but they all are either too simplistic and way to bloated (looking at you evernote).