I wonder if some degree of RPM-dependent shape change could be designed, like F1’s flexi-wing trick that extends its aerodynamic operating range
https://www.savree.com/en/encyclopedia/controllable-pitch-pr...
But these use actuators to mechancially adjust the pitch rather than relying on deformation.
Twisting a few props about a their axes is a lot simpler than the geometry changes that are required acros the control surfaces of a toroidal prop, however. I don't think that would even be feasible
What if multiple props are arranged in a series, akin to how turbo engines have stages with different compression ratios, but instead of a fixed shaft with varying blade geometry we have varying differential rotation speeds between them adjusted based on RPM?