I am no expert. 6-line and dottyback might not go well together. They will fight a lot.
If you are concerned about tank size requirements, follow the tank sizes mentioned on liveaquaria. Wrasses are very active fish and will eventually get stressed out (and die) if they are kept in smaller tanks. I learned this the hard way. Lunar wrasse is a no go in a 55g (unless it is really small, under 4" and you will re-home it later on).
If you are concerned about tank size requirements, follow the tank sizes mentioned on liveaquaria. Wrasses are very active fish and will eventually get stressed out (and die) if they are kept in smaller tanks. I learned this the hard way. Lunar wrasse is a no go in a 55g (unless it is really small, under 4" and you will re-home it later on).