I am thinking you are talking about putting a micro bevel onto the knife? If you are only going sharpen with the ProEdge then the need for a micro bevel is reduced as it is just as quick to sharpen the entire bevel as sharpening the micro bevel.
However if you are planning to sharpen by hand after the initial sharpening then you may have a good case for doing it.
To adjust the angle you use the collar on the stem, to get a double bevel I would start by finding my angles, then marking the shaft so I know where to adjust it, then sharpen the first bevel fully. Adjust to the second and very lightly sharpen again. I would use marker pen on the bevel so I could see the progress on each pass, the proedge is quick so you will want to keep a close eye on what is happening.
OK so that is much easier... find a good bit of bevel, mark it up with marker pen rest it on the belt and just turn it by hand, you are after the entire bevel having the ink rubbed off evenly, adjust up or down as needed Once you are happy that it is at the right angle go ahead with the sharpening through each of the grits, be sure to do both sides evenly, and it doesn't matter much if it is 15, 16, 18.5 or 20 as long as both bevels are the same length and the same angle then the edge is central.
There are machines that will accurately measure knife bevel angles and blade sharpness but not normally in the price range of most people!
Ask any ten woodturners for an opinion on how x is achieved, you can expect at least eleven different answers.