When you all pick up the gusset stitches, do you find that you have to pick up more than written in the pattern and then decreasing those extra ones as well?? Does that have to do with the difference in guage among knitters?
I’ve found this to be true. It doesn’t seem to affect the outcome unless you are picking up way more.
Sometimes people get a little hole when they go pick up the right amount of stitches and go to knit in the round again. To solve this problem the lady at my LYS told me to just pick up one extra stitch and it shouldn’t matter as long as you decrease back to the same number of stitches.
The Sensational Knitted Socks books recommend picking up two extra stitches from each side.
Gauge is not going to be affected by picking up these extra stitches. Gauge is affected by other things, such as tension, yarn weight, needle size…
At what point do you decrease them? Immediately after the round?
Thnaks 
you would just decrease those extra stitches when you do the decrease rounds for the foot, then knit the foot.