All wrasses have the potential to jump, except maybe a leopard wrasse (or similar shaped wrasses). However, the leopard wrasses have a specialized diet and makes most difficult to keep even in a large tank. So I do not know if a wrasse would be a good choice for a 20 gallon with no lid.
Maybe a baslett or dottyback....
I have seen blue hippo tangs (the size of a dime) that would be ok, if you were planning to upgrade down the road. They would out grow a 20 pretty quickly.
I know everybody says that wrasses are jumpers, but I've had several and have been fortunate in the regard of not having any on the rug.
I have a Coiris wrasse in my 29g and he does well w/ the a pair of clowns that reside in it. Got the coris when it was about 3/4" long and he hasn't really grown that much.
All wrasses have the risk of jumping out of your tank, I'm a big leopard wrasse fan I've had good luck with mine on the feeding part, they ate everything that was fed to the tank flakes, pellets, and homemade frozen food. On the jumping I lost 2 after being in tank for about 6 months. If you want a colorful wrasse get any fairy wrasse