Finding a single metric to characterize the logistics curves

I have different shapes of sigmoid curves that I will provide you, and I would like to look into more details if there is any tendency by converting them with Fourier transform. Having the frequency domain with the curves, we can find/detect the peaks (first, second, to at least third or fourth on the frequency domain) to compare each curve and whether there is some behavior between the curves. The details are attached. Thanks.

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