I don't use Mac, but the actual note taking app is not important. The important thing is the global hotkey, so you can make a new note trivially when this global hotkey activates your favorite note taking app.
My hotkey software can also send keypresses to running apps, so beside bringing the note app to the foreground it also starts creating a new note automatically.
Agreed on the global hot key. I use iTerm and it has a global hot key so you can bring it up with a shortcut and then hide it with the same shortcut.