Throw one in and find out is one method.
Technically though you should add the least aggressive first. That being said I added 2 of the non reef safe versions at the same time and they were best of friends. That is until the one became a psychopath and tried to kill him... think he killed my goat fish as well...
Comparability varies, sometimes it works, and sometimes it doesn't. Heck, I even had a banana wrasse once that was invert safe.
Here's what I would do.
1) Google my (wrasse x) is attacking my (wrasse y) and see how many hits you get. That'll be clue one on the success rate.
2) Ask yourself how you would feel losing money if 1 or 2 of the 3 wrasses dies or has to be sent packing.
3) Ask yourself how sure you are you can catch the little ******* if you have to remove it. (took me an hour and a half to get the lunare wrasse out of my tank)
Depending on how you respond to those questions should steer you towards whether you'll try it or not.