What size is the tank? What all are you planning to put in there? How much cover (wood, rocks, plants) do you plan to have? The answers to these questions will provide an answer for the first question.
Angelfish will actively hunt and eat guppy fry. They are specialized small fish hunters. But as they get big, the menu may end up including male guppies. Of course, if you raise them from a small size with the guppies, they'll be more apt to see them as tankmates and not food. Gouramis are more of the micropredator: small aquatic invertebrates for the most part. Dwarf cichlids of the Apistogramma genus are also specialized for hunting fry, but these never venture far off the bottom of the tank. I think your best bet is a school of mid-sized upper-area dwellers such as black neon tetras, penguin tetras, gold tetras, zebra danios and related fishes, golden killifish, or something else along those lines.
If it were me, I'd take the chance with a few angels.
"One day...one day, this path will lead us to the White City, and the tower guard will take up the call: the Lords of Gondor have returned!"
–Boromir, The Lord Of The Rings