Thanks for questions!
Stitching multiple lines at one time didn’t feel like a huge jump from other composite stitches, like those for Norwegian. There was an extra level of difficulty using the very fine Meisi thread, since it proved too uniformly waxed and smooth to unwind and too thin to pierce with the harness needle for a “lock”. I would definitely recommend cutting off some additional extra thread, to make sure you always have a nice, long tail through the eye of each needle.
I can’t say that I’ve timed either one line at a time or three at a time. Since I’ve had so little practice, I don’t imagine doing that would tell me much at this stage, since I’m probably just getting faster overall.
What I can say is that I had no lingering questions about whether I got the stack-up of threads through the holes right. Sewing one line at a time, one on top of the other, I would manage to get the lines to lay right in the end, with some adjustment. But I was never fully confident I got them stacked right in every hole. I only got that confidence stitching all the lines through each hole with the threads still loose, then pulling them tight.