A related (?) problem… I have tried to use Plots to do a 3d surface plot with contours (useful, e.g., in illustrating optimization problems). However, I was not able to freely choose the z-position of the contours – this seems to be hard-coded to z=0. If the minimum value of f(x,y) is “small” (close to zero or lower), the surface plot will often hide the contours. When I tried to learn Matplotlib some years ago, I found it was relatively straightforward to set the z-position of the contours, and I’d think this is very useful also in Plots.
[OK – perhaps this is possible in Plots – I just haven’t found any documentation of it.]