Well, that's the beauty of the Freedom model--the output is adjustable. Since you're interested in preserving night vision, the question about brightness isn't really that important. All of the different models are bright enough to affect your night vision to some extent unless you turn down the output.

So, unless I'm misunderstanding your intentions, sounds like you can just get a turquoise (since you don't seem to want a red one) and dim it down to whatever level you think is appropriate to preserve your night vision. The turquoise and the white model will both run on 2 x 2016 cells.