what scott said about feeding, if there is a flow on, there is no need to feed UNLESS you are establishing a package, a nuc, a recent divide, or you are wanting bees to draw foundation. as soon as the foundation is drawn, pull the feed, otherwise, like scott said they will store it in a super. you don't want syrup in your honey supers.
"...and for nucs that fall kinda in the middle?"
zweefer, a healthy nuc will surpass package bees, in general. you want to get the nuc built up in two deeps before putting any super on. if you have nothing but foundation, the likelihood of them producing any honey for you to take off, don't expect it, and even with drawn comb to give them. most packages and nucs will spend the season building up.