In contrast to the other replies on this topic, I believe it is possible to plot spectral efficiency vs signal to noise ratio – this is exactly what Shannon’s law is all about.
“the maximum attainable error-free data speed, in bits per second (bps), is a function of the signal-to-noise ratio and bandwidth”
See figure 7 in the following as an example…..
https://www.dsprelated.com/showarticle/136.php
