Well what is the right angle? You may ask. It depends, on the steel and the task. If you go buy a cheap knife from the grocery store and take it to your water stones (I spent my college years doing this) you can achieve a razor sharp edge. But, you will find that the softer steel will deform and dull quickly. A knife with softer steel is better served with a slightly thicker edge that won’t be as wickedly sharp, but will cut all meat and vegetables for much longer, due to the more sturdy geometry of the edge. My knives are made from 52100 high carbon steel which after heat treating it, can perform very well at much thinner dimensions unlike economy stainless knives.
After the capabilities of the steel, the intended purpose of the knife is important. If you are only cutting raw fish or delicate garnish then you want a thin edge that won’t tear or deform what your cutting. If you are mainly cutting potatoes and onions for dinner with the occasional whole chicken to break down, a blade with a less acute edge will be able to withstand the repeated contact with your cutting board and still be serviceable for a reasonable amount of time. Obviously, that depends on how delicately you treat the edge. Unless your cutting bone, its not typically the food that dulls your blade but rather the surface that you’re cutting on and how hard you bear down on the edge. Cutting on glass or metal surfaces has a distinct and horrifying sound! Don’t do it! Wood or plastic cutting boards provide a great surface to cut on. Going back to sharpeners, for those reasons I think most automatic/electric/etc sharpeners are very limiting in the edge that they can provide you with. One geometry doesn’t fit all tasks. That’s why most people that spend a lot of time cooking have more than one knife, all with slightly different edge geometries according to the task at hand.
The second thing to consider after the angle of the edge is the polish. The polishing is just grinding away smaller and smaller pieces of the steel. This allows you to bring the blade down to a smaller cutting edge than you would using a coarser grinding material. I recommend a medium coarseness and fine if you are going the route of stones. The level of polish is up to the user. A knife sharpened with a coarser stone will have a more jagged structure on the microscopic edge. This is great if you are cutting tomatoes of other soft fruits and vegetables with tough skins. For butchering and cutting meat, a finer polish will perform better over time. If left with a coarse edge a butchers knife will gather fat and sinew in the edge and require much more frequent honing to remove it. A polished edge will be much finer and therefore less affected by the smaller accumulation of tissue.
As anyone who has bought a knife from me already knows I happily offer lifetime sharpening services. But I encourage you to experience the difference in a properly sharpened knife and the satisfaction of doing it yourself.