This is a comparison of rendering settings and you can see the difference of each setting clearly.
I used one of my old Revit project and rendered for each and every settings.
Revit has four default settings
As you can understand best should be the best. But it is wasting time to Render in Best quality. It takes hours to complete the rendering in Best mode.
So I recommend Medium and high as you can see in below Renderings.
But carefully select the DPI (Dots per inch) you want. I recommend 300DPI for your renderings because for 600DPI rendering takes much more time and 300DPI gives a good image as well.
Check below images and get an idea.