I love the formatting, pictures, and cautions. Good visual flow too. I'm a bit surprised it doesn't go into the technical aspects of what's going on with the transfer functions, which op-amps/ADC are used etc.

Aren't op amps sort of interchangeable here? Provided the correct temperature compensation, they all are highly linear, have a few MOhm input impedance, etc.

Same with ADCs; the signal in not particularly high-frequency.

What am I missing?

I've used those and they are fantastic and very easy to wire up!