I haven't done all hexes, but I did a Jack's chain which is hex, triangle and square with entirely set in seams. Each shape finished at 3" on a side.
I machine sewed each seam and left a generous 1/4" unsewn at the beginning and end of each seam, just as if I was hand sewing. I wouldn't have wanted to do it with hexies that were smaller than 2" on a side.