I usually recommend people run the larger size tube. If it’s not too big to install, then it will stretch less and be slightly more puncture resistant.
However, why are you getting into TPU? If it’s for weight or rolling resistance, then definitely run the smaller tube.
I don’t like using tubes on the end of their spectrum; just bc the box says it’ll fit, doesn’t mean it always will. Surely there’s another brand of tubes with a better size range? That’s my best answer tbh.
(Are tpu extra stretchy? 18-32 is a crazy range by butyl standards)
Based off all that, I’d run the 18-32. Besides, assuming you’re not buying in bulk, and you’re not doing rural bike-packing, then getting a flat or other mechanical won’t be too catastrophic or costly. Try em out a lil, and report back on how you like them :)