The 1x8pin connector will supply up to 196w theoretically. Most of the GPUs are 170-180w with a single 8pin connector on them. The 1070s are extremely low on power consumption compared to most cards. Equihash for example, you'll see about 100w used. You have plenty of room for overclocking if power isnt an issue. Otherwise, lower the TDP and enjoy the cold cards.
To be honest, my comp at idle uses 95W, with 1070 and 970 at overclock it uses 450W, which seems damn high to me.
At underclock it goes down to just 410-420W, which is not really meaningful improvement, given how much hashrate is lost (15%).
Some days I managed to keep it at 370W stock clock, but I have no idea how I managed that, tbh.