As a rough idea it should include some functions like in Drawboard or rather the Apple App Notability. But there is no need to include such complicated functions as "speech to text" or something like that in the beginning.
It should include roughly: Pen writing input (which is obviously the most important function for this note taking program, because it should also allow to draw something), insert squared sheets (like 5mm cased), different pens like marker and colours, something like a snipping tool, straight line tool. These would be the importest functions in a first version. But maybe there is some follow up work that includes other functions. :)