The DFU uses a spring or spacer of some sort to apply preload.
I don't like the spring versions as they will give backlash at some stage.
The spacer versions can be hit and miss too, unless they are made with extreme precision.

I prefer the double-nut version which is manually adjusted with a very fine screw-thread. You wind the second nut out (or in) until you feel some resistance, then you check how easily the ball-screw rotates in the assembly, and fine-tune until there is just a slight drag. That seems to give close to sub-micron backlash. Then you have to lock the adjustment of course: not with a lock nut but with a toothed washer.

However, this only works with a good uniform ball-screw. If your ball-screw is worn significantly in (say) the middle, then what is tight at the ends will be loose in the middle. But then you need to replace the ball screw anyhow. You could keep it going for a while with a spring-loaded version, but with reduced accuracy. TANSTAAFL

As for a zig-zag packing - forget it. Normally the balls in a ball-screw are not jam-packed together (and should not be so!), and the grooves should definitely NOT have that sort of slop anyhow. Does this mean those cheap poor-tolerance ball-screws should not be used in a CNC? Correct. They may be good for motorised window-openers, but not in a CNC.

My 2c
Cheers
Roger