In the video the opacity of the annotations were decreased, but I cant seem to see an option like that in blender 2.80, only to change the thickness of the lines and the color, I guess I could just make them more gray but.....
So...….. hhirvios I am pretty sure that the Grease Pencils make use of the alpha channel for opacity. But the regular "annotate" pencil does not have that ability to my knowledge. You can however pic what surfaces the annotate pencil writes on like a hidden plane aligned with the view and going through the 3D cursor, or tied to the viewport display itself always or snapped to the surface(s) of a 3D model.
Let me just say: The new grease pencil is "sick" and has so many new and cool features! I honestly have not used it much yet because I am still kinda new and easily distracted in my training but this video from the blender dev team shows the ability of what it can do now in blender 2.8...…..blew my mind.