I don't like to go more than two any direction, but I'm not any good at confetti. Basically posting to see what everyone else says!

I tie knots on those lone, far-out stitches. Or I know some who use the pinhead stitch. Believe me, no one knows there are knots behind the confetti stitches. And, sometimes, depending on the pattern, I will use a bead.

I believe you can carry your floss up to 5 squares. I personally determine that if I carry it across the back of the fabric where there is no stitching, if the floss will show through to the front of the fabric.such as having black floss being carried across the back of white or Antique white material.
There are no "stitching police" , so I've carried my floss further than five but I keep in mind not to carry a dark floss under a really light floss.

4-5, usually. I've used 6 when I didn't trust the floss to stay put. Depends on the floss, type and number of threads, location of the stitches, whether I'm using a hoop or scroll frame, or "in hand"...sometimes mood and you just get a "feeling". :) i get nervous about the weight of beads... :)

With confetti and beads I have sometimes left a "tail" to be stitched over by an adjoining color...whatever works for you... :)

Many of my larger project's are confetti type. I try to use the floss to the bitter end in all my projects, waste not run out not especially with some kits. That being said--I "carry" my thread as short a space as possible, on back of project, I prefer not to knot when ending but slip under a few stitches to secure floss end. My rule of thumb for amount carried is: a few stitches short of the fabric count being used--14/18 aida is my favorite so 14=no more then 5/7 18=8/10. Worked so far!!!

Many of my larger project's are confetti type. I try to use the floss to the bitter end in all my projects, waste not run out not especially with some kits. That being said--I "carry" my thread as short a space as possible, on back of project, I prefer not to knot when ending but slip under a few stitches to secure floss end. My rule of thumb for amount carried is: a few stitches short of the fabric count being used--14/18 aida is my favorite so 14=no more then 5/7 18=8/10. Worked so far!!!

No more than three, is my rule. If at all possible, I'll weave the floss under existing stitches. My front might no look all that good but I always get compliments on my back. :) I dislike a messy back. Sometimes it can't be helped, however when possible I try to avoid it.
I have to attach several beads out in the middle of nowhere on my current project and am wondering what would be the best method. I'll have to use Rainbow Gallery metallic and don't know if it is suited for the pinhead stitch. I have to do a few tests in an inconspicuous area. Maybe I'll use regular floss in a goldish color. This hobby is turning into a headache! LOL