When light tracing is activated it does not show up in the render info, it will only display "PathCPU" or "PathOCL".
I have not noticed any difference between Sobol or Random sampler regarding the "overexposed caustics" problem but will test that.
These pictures are just examples to demonstrate the various differences in caustic brightness with the hybrid engine, which should show consistent brightness under all conditions IMHO.
Edit:
I just played around with different combinations for half an hour and everything worked normally until I changed hybrid partition from 0.9 to 0.8, resulting in too bright caustics. But after the next start all is well again
It is a really nasty thing because it can not be reproduced with certain settings.
I don't even know if it happens with Sobol only because whenever I switch samplers the statistics window disappears with reboot and I forget to reactivate it when making a screenshot.
Edit2:
Just caught it from Blender with Metro sampler.