There are a lot of ideas but main ones seem to be:
(a) Fuge before skimmer so the Fuge gets all the nutrients & waste from the DT to be healthy and function as effectively as possible;
(b) skimmer before Fuge because the skimmer is basically mechanical filtration and belongs first in line. I saw a thing where Ryan from BRS was talking about this and said something like sure your refugium may be faster growing or better looking being before the skimmer but what is the point of the Fuge, are you growing a good looking Fuge, growing chaeto or looking for nutrient export, better to just get as much out as possible with the skimmer and then let the Fuge make that cleaner water even cleaner;
(c) some people run fuges seperate to sump or last in line in the sump. They put it last so you can grow pods and other good stuff. Being last in line, the pods only have to survive the return pump to get to the DT. This can be a good idea if you have something like mandarin dragonet fish but you can also rotate pod farms between Fuge and DT to feed.
Personally I went for (b)
