In general, I'd say the ideal geometry of a knife is whatever you happen to like NOT including that v shaped edge. That's the part that doesn't fit but it's useful because it gives the edge strength. Without thinning, that little (and relatively thick) edge takes over the overall geometry of the knife, making it closer to the geometry of an ax than a tool for cutting food. That little v should always be minimized. This is the idea with microbevels, too. You sharpen the knife the way you want it to cut but find the edge is too thin to withstand use so you make the edge thicker which is very bad for cutting but since it's tiny, it does not contribute significantly to the overall geometry of the knife.
By far the most common mistake is not removing enough metal. I've seen knives bought that were supposedly thinned many times over years of use with the original grind marks from the manufacturer near the edge bevels. If you're thinning correctly, most of those grind marks will be gone after one or two thinning sessions barring low spots on the grind.
After that, there's thinning too much (this is rare), not thinning both sides appropriately, taking too much off the softer cladding vs the harder, more wear resistant core, rounding shoulders, I'm sure there's more and variations depending on the type of grind.