Well see, a lot of the answer depends on a few factors
Size - These guys are aggressive by nature, but until matured, can fall prey to other aggressive carnivores. Likewise, when matured and fully grown, being that they are known bullies, they can pick on smaller tank mates - even eels, should they be smaller than the wrasse.
Tankmates - Since these guys are carnivores, anything they can eat - they will. This includes animals such as crustaceans, snails, shrimp, starfish, smaller fish, worms, and other invertebrates. So if you currently have a nice cleaner crew, you can pretty much kiss it goodbye as these guys grow.
Decor - These guys get big. With that, they need space, and all items in the tank must be secured, as another nick-name for these guys is "Rockmover" - which they do very efficiently. They will move corals and rearranges the rocks in the aquarium to find food, so it's usually not advised to have a reef tank when investing in these guys.
When keeping them with eels, that depends largely on what type of eel and how big they both (eel and wrasse) are. Eels are canivores and opportunistic. The aquarium should also have a tight-fitting lid to prevent it from jumping out - which would happen as it's mode of "Flight" from a predator.
What eels are you looking into, and what all do you have planned for your tank?
