Hi Nikki,
Second question first. I have heard the same thing - that the singles should be taken from the bobbin for measuring twist. Personally, I don't see any difference in taking it from the bobbin or pulling it back through the orifice. Now, it would make a difference if the flyer turned while you were pulling back through the orifice because one twist would be removed each time the flyer revolved. The bobbin turning does not add or subtract twist.
How you wrap the yarn around a wpi gauge would make a difference in the twist.
First question. I hope I'm understanding what you're asking.
5 or 6 singles plied together would be a plied yarn with multiple plies.
If you were plying 3 - 2 ply yarns together it would be a cabled yarn because you would have to ply them together using the twist direction that was opposite of the twist direction used to create the 2 ply yarns. But, unless the 2 ply yarns were over plied, you would first have to add more twist to them to make them work well in a cable yarn.
