Does it allow you to fix the angle of the edge? I have used a number of sharpeners that don’t and I am just not experienced enough to get a consistent angle every time.
Yeah I don't think I've ever used a sharpening system that let me go from "well at least it cuts things now, that's better" to shaving-sharp.
There do seem to be systems like this which basically hold the blade at a fixed angle as you drag it over a diamond surface.
Part of this is because it takes a lot of work to get a blade shaving sharp, especially hardened tool steel. However much effort you put into it initially, quadruple it. That's why professionals use machines to sharpen their tools.
There are plenty of angle guides that’ll help you set a specific angle. They tend to be object specific though because they typically involve clamping the blade to hold it in a fixed position. For example the Lansky and Worksharp Precision Adjust work for knives but not chisels. The Veritas Mk ii works for chisels and planes.