I'd say that unless you are working in the bigger gauge or getting something published, 3 link is over the top. A cosmetic one on the front of a steam loco is fine, but to the rear I'd use a conventional slim line coupler, or even a small brass bar for the wagons/coaches to couple up to.
Choices here. Photos should self explanitory.
http://www.scalelink.co.uk/acatalog/Smiths_couplings_for__OO_.html