That flight is in November so a lot can change before then. They will be selling PS on this route once they are certain the A333 will operate it. If you book C+ hoping to get a free PS seat without applying the GUC, DL will change your seat to the regular C+ cabin with no notice once they begin selling the PS seats (turns them red on the seat map).
I would probably wait until PS opens up for sale. At that time, the more typical amount of Z inventory, and GUC upgrades at booking, will be easier to find, and you can assess the value of such because you will know the PS fare.