The thing about GIvsAA balance is that you will end up with an image with almost identical quality in given time (e.g. 5 minutes) regardless of the settings you use.
Higher GIvsAA = better GI, worse AA
Lower GIvsAA = wrose GI, better AA
There is also LSM which controls the quality of light sampling (mainly visible in area shadows)
For quick previews (as far as I understand that's what you are after) you could set LSM to 1, and GIvsAA to ~8. That should give you faster feedback (more passes in less time), but quality will be worse in the long run.
You can also save some time (depending on the scene) by lowering UHD Cache precision to 0,1, but remember to revert it for final render. :)
Also:
https://coronarenderer.freshdesk.com/support/solutions/articles/5000526159