Though scant comparison with yours, my twin GTX 750 cards thrive on vol-bounces = bucket-size = 1024 for Superfly renders.

But, if scene is too complex, with detail and/or wide-angle, so test-render black, drop that 1024 by binary stages to 512, 256, 128 then 64...

Um, is your 2060 a 'type 2' with the extra RAM ??