How to change the default font and size in Notes on El Capitan?
And the keyboard's plists of PressAll also can no longer be modified to add the new accents.

Tip: You do not need to modify the default font and size in Notes. 

To change the font, you can select all or one sentence and press Cmd + T. 

To change the font size, you can press Cmd, Shift and + at the same time to increase or Cmd + - to decrease the size.

Another tip: If you want to use the user font in Notes in OS X, please, install and use AnyFont in iOS to install your favourite font in iOS.