None are difficult. Just be aware of size and aggression.
Thalassoma wrasse are very energetic and can be aggressive. However they are very tough and easy and come in some great color combos. Here’s my T lunare
Dragon and seagrass wrasse are the most interesting fish. Mine is like a wrasse, blenny, and goby combined. However they can wreak havoc on your sand and rocks and can also be aggressive. Best pest eaters though. Here’s my dragon
Coris are big and can also move rocks around. What I love about them is they go through very distinct life/color stages. Here’s my juvenile red coris. C gaimard
Finally Halichoeres is a massive genus. They are by far the most peaceful wrasse on this list but the smaller species may be bullied by bigger fish. Most are easy and very available though. Here’s my H marginatus