First off, let me say I'm not particularly big into these cameras so I don't know the ins and outs too well.

You'll get less of that randomness (color/contrast-wise) with regular film unless you find some good expired film. The lomography film supposedly has that already. If you try it with regular film, go with something fast (probably ISO 400 or higher) just because they tend to have small fixed apertures. That Konstructor has a fixed aperture of f/10.

I have two similar cameras, both gifted to me: a Recesky DIY TLR (which admittedly was pretty fun to build and use for a while), and the Sprocket Rocket, which I haven't even gotten through a roll with yet.