Those prewelded wires from FT are cheap, the only thing that concerns me about them is the resistance wire is black, and has a sort of rough feel to them- not glassy smooth like Kanthal or NiCr wire that we usually buy. And there have been reports from users of those premade wires of off tastes, sore throats and other allergic-type symptoms. Now, I don't put a lot of stock in such things but just the same, there's some peace of mind in making them yourself, and knowing exactly what went into them.
Silicone insulators are overpriced IMO. That said, silicone insulators like the original Kanger-type (and presumably the ones from LV) do hold up better to heat than the cheaper rubber ones in my experience, but they're still not immune to scorching from a hot leg. But you can use any insulator- even the cheap rubber ones- if you also use NR-R-NR wire for the coils.
A friend of mine picked up a variety of the FT premade coils. They are indeed black and appear to be made from Nichrome instead of Kanthal, which does cause trouble for anyone with a nickle allergy. I have used my friends coils in the past without any issues, taste or ill feelings. The problem was he ordered coils that had either a 1.5mm or 4mm ID, as he didn't quite know what the Depth measurement in the description referred to.
It was just a suggestion and for $2 if you don't like them, bin them. I suspect that half the welds might not be good, but they are just cheap Chinese coils...