Overclocking for the 1070’s can be done with software like MSI Afterburner. There’s a thread here with some specific tweaks you could try. I can’t find the exact post at the moment. I’ll post it if I get a chance later.
I’m currently running a 1070 at 80% power and getting around 480 Sol/s. As for your motherboard, there have been some issues with the Z170’s getting more than 4-5 GPU’s running, however there are numerous guides online with detailed instruction on how to get past that issue. Sometimes the CPU plays a part in that as well.
Some threads to get you started:
Either way you look at it, you’re in for a lot of reading.
