From a cyclists' perspective - a good modern bike chain transmission is very efficient - percentage efficiency is somewhere in the high 90s and has been for decades.
(From anecdotal evidence: endless debates in cycling over the years, about various inventors attempting to "improve" the design of the bike with belts/pulleys, conventional gears, even things like propshafts etc. Such alternative designs sometimes have useful features, but they haven't significantly improved overall on the strength, efficiency and light weight of the modern chain & sprocket.)
As far as application to robotics is concerned - it will help to make sure everything is mounted well, not in a flexible way so things cannot deflect under load, and the gears and chain are kept in a reasonably straight line. These are the way bike components are mounted too.