Ok so I did the my first successful 1500 strapping on my two rx 470 4g. One is at 23 mh/s and the other 22. Up from around 19.5. Is that good? What can I do next for more performance!
1150 MHz core clock, 2000 - 2100 MHz memory clock should get you to ~29 MH/s stable with a good timing strap bios mod. Also run HWinfo 'sensors only' to check for memory errors and reduce the memory clock by 25-50 MHz until there are no errors.