I have always connected the “spacer-wire” at the mains plugs side together with the GND wire.
If there is a EM field inducted from the “life” conductor to the spacer, this will be fed to ground.
Main reasons I do this are, more equal spacing between life and neutral and it gives the whole construction a more solid fit. The Jantzen wire for neutral is not as easy to work with as if it would be with a solid core wire.
No, in this construction I do not cover the life wire with anything else.
I have made more than a dozen different Helix PCs with different wires and they all sound slightly different.
This Design is with my ears and my equipment the best compromise in terms of “sound” and “construction”.
On the “air” (wire without insulation) design and on other designs I had used 2 Teflon tubes (6mm and 12mm) to create a kind of “spacer” to keep the neutral away from the life conductors.
I think the coiled GND wire is at least equal and easier and more cost effective.
I use a 3:1 ratio.
I used different plugs, and these “sound” more different, than some of the different constructions.
The SonarQuests silver plated are very open. On some applications I prefer the Furutech FI-15 (G) IEC connector, as it is easier to work with and has a more “solid” sound signature. And for Schuko plugs I used either SonarQuest, Wattgate or Hifituning. Later 2 are easier to work with.