#1 ) Yes......The screws on a sebenza 21 tighten down and when they are snug, everything is smooth and the knife it set. The tolerances are that tight. No need for lock-tite. Its how all the sebenzas were designed before the 25 came out. The 25 took the adjustable pivot of the umnumzaan and incorporated it into the sebenza. This is where the lock-tite came in as the pivot is adjustable. Just a small turn will either make the knife tight or looser. The inkoso is similar to the 25 and zaan in that regard. The 21 and what preceeded it is simpler in design and easier to take apart on the only needing one simple hex wrench........As a note, I bought my 25 when they first came out and still have yet to take it apart and I carry it OFTEN. No need to constantly take them apart. Many I have never even done so that were purchased new. I only do it initially when I buy used ones. But Yes, the inkosi uses the adjustable pivot like the 25 and the zaan that uses lock-tite.
#2.) Its just a personal preference.. I like the older original 21 design and the regulars far more than them even. Both the 21 and 25 ( very similar to the inkosi ) slice and cut very well, regardless of blade thickness and design. The insingo is a hell of a slicer though I must add. I DO like the thicker blade of the 25. But If I had to pick ONE, It would be a regular hands down followed by the 21. I do love my 25 though. As for zaans. I sold all that I had. Dont have an inkosi as I have a 25 and to me, they are the same, only a slightly different version of it.
#3.) Quality & Customer Service. Both go hand in hand and is what makes CRK who they are. Its what has kept me coming back for well over 100+ CRK's.