I second this. I don't see a good reason to allow a custom rendering resolution with FSR 1.0 but force a dynamic resolution for DLSS users. It would be better to have it on by default but allow us to disable the dynamic resolution and pick whatever rendering resolution we want with the existing "3D Resolution Scaling" slider if we prefer that option.
I know I would prefer to force 70% or so and save a bit of energy, also get a cooler room in the summer.

Adding more options for the FPS threshold when using dynamic resolution would also be good for people who want to play with higher framerates. Could allow to target 90, 120, 144 and 165 FPS