How to begin to Undervolt AMD GPU's + best settings performance

Hi, need some help. i like to undervolt my AMD gpu 's+ best settings for zec mining. gpu's saphire 280x 7970, 7950. (not all hynix), Asrock 970 extreme4, 8gb memory. using claymore's zec miner. amd driver 15.12 mining 280/7970 185 sol, 7950 170 sol. faster is possible. too much watt...): test on win7, win 8.1, win 10, what is best? (win 7 max 4 gpu, more sol)

Best easy option?. 1. Custom bios? 2. Hacked Modified Memory Strap 3. overclocking tools 4. claymore's -mclock -cclock setting.
what to do, not to do. for newbie Thx appreciate your help!

  1. New bios/ Custom bios created by other zec miners)
    https://www.techpowerup.com/rbe/
    https://www.techpowerup.com/vgabios/
    https://www.techpowerup.com/vgabios/124572/ati-hd7950-3072-120706 etc

  2. Hacked Modified Memory Strap BIOS Database for ZEC MINING
    https://bitcointalk.org/index.php?topic=1676474.0;all
    http://www.overclock.net/t/1554360/tahiti-memory-timings-patch-for-hynix-vram
    https://forum.zcashcommunity.com/t/hacked-memory-straps-for-zec-mining-90-sol-s-on-7950-7970-280x/7928

  3. Overclocking tools
    http://www.overclock.net/a/getting-started-with-radeon-hd-7970-overclocking
    https://forums.anandtech.com/threads/how-to-enable-core-voltage
    http://www.overclock.net/t/1609782/watttool-a-simple-tool-that-combines-overclocking-with-vrm-monitoring-tweaking-for-rx-400-series
    Setting??:
    gpu 1070
    mem 1500
    vddc 1.094

  4. Claymore's: -mclock 1900 -cclock 1300 setting
    1150/1450 -mclock 1200 -cclock 1500 ?
    Best clock settings for:
    Saphire r9 280x 1500/ 1150 ?
    Saphire hd 7970 ?
    Saphire hd 7950 ?

Bat.file

setx GPU_FORCE_64BIT_PTR 0
setx GPU_MAX_HEAP_SIZE 100
setx GPU_USE_SYNC_OBJECTS 1
setx GPU_MAX_ALLOC_PERCENT 100
setx GPU_SINGLE_ALLOC_PERCENT 100

ZecMiner64.exe -zpool zec-us1.dwarfpool.com:3335 -zwal wallet.name -zpsw x -cclock 1100 -i 6 -tstop 81 -ttli 79 -mport 0

GPU_FORCE_64BIT_PTR 0
GPU_MAX_HEAP_SIZE 100
GPU_USE_SYNC_OBJECTS 1
GPU_MAX_ALLOC_PERCENT 100
GPU_SINGLE_ALLOC_PERCENT 100
ZecMiner64.exe -zpool pool -zwal wallet.name -zpsw x -i 4 -mclock 1500 -cclock 1200

I just drag the slider all the way to the left on MSI Afterburner

Ok thx, the same for Sapphire TRIXX? MSI Afterburner best tool

Ya but it might crash if you undervolt it before you start mining I usually wait for a few shares before undervolting