The little "knives" are a sharpener and a smaller knife (for god knows what.)
The sharpener (chakma) is used to slide along the edge and push back the metal to restore the edge. These were designed in a society which had no access to sander, files, diamond hones, or belt sanders.
The little knife (not so little in some cases, they are proportional to the primary blade itself) is a karda. (K=knife, c=er, uh, something else).
Keep in mind these are
tools which came to be used as weapons.
Dan Koster's (Pendentive) khukuri dynamics cad/cam drawings of the various shapes can give you an idea of variety, and differences, but the knives need to be held to speak to you.
http://www.himalayan-imports.com/faq/physics/Khukuri_Dynamics.html
The AK is the chopper designate, but so many others can also perform this task. There is some discussion about it, but bone is usually too dense to be "cut" by a knife...even an H.I. khukuri. (I did it, and had to re-profile the edge where chips came out. This was deer leg bone, and was more crushed and fractured than cut. The ribs of a deer are flexible and porous and can be sliced through.)
Then you get to weight, length, and general design. The longer the blade the greater the leverage you have; the heavier, the more impact. But there are many variables, including your own physical dimensions which affect the utility of the tool.
Take your time. Go through the frequently asked questions thread (FAQ), and as you see a model name, use the "search" function on this forum to see what folks have had to say about each. This is a forum founded on honesty and candor, as well as respect and tolerance.
Enjoy the learning curve, then think about what you may want to purchase.
Be well and safe.