I have a few Gigabyte RX580 8GB Gaming with modded BIOS, but with Cast on Heavy, they normally do not go more 890/920hs, sometime they spike above 1000hs for a few seconds but that is all.
Yesterday while I was testing SRB (with intensity 59) they went at 970/80 for a couple of hours and stable. Then when I did further tests, even with the exact same settings, they never went more than 870/890hs with SRB.  I normally use GPU 1300,1050 and Memory 2150,850 with OverDrive Tool.

Then I have a rig with few Vegas 64/56 reference cards, with Samsung memory, but so far I get better results with Cast rather than SRB. Both CAST and SRB are stable, although I have 7 months of experience with Cast and I can have it running for consecutive days with not HS drop or crashes. I heard that SBR is also very stable but I have not run it more than a day.