No drawstring or elastic and it is a straight cut. Does not bell out at the bottom, should be okay if you get the correct size, not too large.
No, nothing at bottom, but not a problem for me, 32" waist, medium size vest. PNW climate moderate, so vest great here, best under hoodie on cooler days. Care needed as zipper flap can get into zipper.
This item does not have a drawstring or anything else at the bottom hem.