One Piece is my all time favorite anime, DBZ is my 3rd.
I can tell you are not that far in, It's still a bit slow at the beginning of the grand line but Just wait. its going to get much, much better. And by the time the war happens I could imagine you'd say it's the best too
Yes Luffy, like Naruto and many other anime characters is based off of Goku
Pull that card? If you don't like Devil Fruits then stop watching, its a main part of that world and ALOT of pirates and marines will have different abilities because of them, on the grand line almost everyone with a 50 Million Beli or higher bounty has one. Though some incredibly powerful people don't have them (like Shanks) and I can't tell you why without spoilers, but there is a system of strength like Kai in DBZ or Chakra in Naruto that's introduced much later on. Enjoy the easy going pace and weak fun villains while you can because it gets much more intense.
