The frame rate issues in the PS4 version of Far Harbour can be fixed by simply re-downloading the DLC. It now runs better than the Xbone version, but at the expense of some graphical effects - the fog, which caused the slowdown to start with.
Contraptions allows players to build elaborate Rube Goldberg-type machines. You won't need to wait long to get tinkering, since it's out next week.
Vault Tech Workshop will allow players to build their own vault and conduct their own experiments, and is out in July.
Nuka World opens up an entirely new area, much like the recent Far Harbor DLC, but this time you'll be exploring a town set within the ruins of a Nuka-cola theme park. Nuka World is slated for release this August.