Pretty much explains itself.
Duece, slowest serves are out wide, over the higher part of the net.
Duece, faster serves up the middle, lower net.
Ad, his slices are hit faster, as the net is lower.
Ad, into the body, with his toss atop his head, serves go over a somewhat low part of the net, so can be hit fast.
Ad, serves out wide to the backhand of a rightie, Fed has a great twist serve that is faster than his slice and has more loop action clearing the higher part of the net.