I don't know 12 speed bits that well, but having looked at one-by for touring I'll make a couple of observations...
Single chainrings are mostly a mountain bike thing. That tends to mean low gears on 26 / 29 inch wheels. Your 24 inch will exacerbate that, so trading low gears for high isn't what manufacturers have designed (marketed) for.
That ought to mean that 24 inch wheels will get a typical road spec down to something sensible. But roadies seem to favour doubles still.
After market chainrings may be your friend. For instance, Absolute Black do one-by chainrings with 40 and 42 teeth.
I found it really hard to get the range I wanted from one-by. It seems to be a solution to a different problem than a bike that can work well both with and without luggage across a range of roads. But if it works for you, that's nice.
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