Pretty much, you're right. A lumen is a measure of total light output. So given one light with 400 lumens and two lights with 200, the the two will product the same total light output as the one. If all three have the same light distribution pattern, the two will work like the one...except that with two you can aim each differently if desired. And you have redundancy. If you think that's worth having the added complexity and dealing with two light setups, go for it.