I could've sworn the standard gain was 32db, so I checked the Naiant website: it is 32db, but it also starts at 6db gain, not 0. So the standard gain range is 6-32db, with the optional input transformers, that would be an 18-44db gain range. Again though, check with Jon, maybe he reduces the gain from the op amp gain stage to adjust for the 12db gain from the tranfos.
Also, I don't really think the issue is overloading the input, from Naiant's published specs, even a hot mic fed into a input-tranfo littlebox at deafening concert levels will not overload. The downside from what I see is Jon's own testing that shows that "professional" mics with a 400 ohm impedance will have a 10db rolloff of 20hz bass frequencies when using input transformers. As Jon notes, this will be somewhat less for more typical 250 ohm impedance mics, but still the downside of input transformers is a loss of bass. And if you want the "transformer sound", you'd get that more from output transformers.
I'm really just parroting back what Jon has said if you dig through his posts, but the summary seems to be: if you want high gain, low noise amplification (like for nature recording or foley effects gathering), get input transformers; if you want that transformer sound, get output transformers.