Delpo I think has super stiff wrists, so he gets much more slap out of limited lag.Sock and it's not even close.
Check out using slo-mo the "forehand" at 5:28 in. This is not a tennis stroke so much as a ping-pong shot. And it's more representative of his FH form than outlier.
Delpo is not very wristy and certainly not in the same ballpark as Sock. Try the shot at 1:28 in, again, slo-mo. It is a seriously hard hit forehand and representative of his FH form and it is not a wristy shot: