It will be great to check first what extensions are present and then decide what to use.
For example, NVidia driver 535.113.01 for Linux doesn't support VK_KHR_RAY_QUERY_EXTENSION_NAME.
Also request: change RTX On / Off based on chosen graphics settings, i.e. on runtime (probably with scene reload).
User scenario: I download same app and launch it on high end PC and low end PC without changing configs or anything. I get RTX On and RTX Off depending on where I launch.