underclock and/or undervolt
also, your other components draw power as well, not just your GPU, so if your system total is 700w then your gpus should account for ~650w of that
can i uderclock or udervolt in afterburner , i there is other way

You cant undervolt the GTX 10xx series, they are locked by nVidia. You can underpower, for example I have the 1060 3gb cards and I have them running at 85 power in MSI and get the same ZCASH SOL/s as 100 power in MSI afterburner.
i tested this and i get at 75 power the same like 100 and 50w less nice , but still how i can get under 100w pro card ?
i have tested on my 980 ti on 75 power it the same like 100 . but can i go lower ?