I have a Janome & a Bernina, I keep one threaded with light colored threads & one with dark colored threads. Both are 3-4 threads and work great. I like the weight of one to be heavier if I am using bulky fabric. They get going so fast the heavier it is stays in place better! My first one was a $40 one from Walmart that worked but would jump all over the place needed a clamp to hold it down. I gave it away to someone who didn't know whether they would ever use a serger, but interested in trying.
Debs wishing I had more time to play on them!