I usually go with -500 Memory Clock and then raise the Core Clock up to +75 (or higher/lower depending on what your card/setup can handle). Either way, that will make a HUGE difference in the mining speed results on your 1070 cards!

There are tons of lists online with recommended OC settings depending on your card and the algorithm - you should look around for a good one, as it's a nice tool to have for mining (especially if you regularly switch what you're mining based on current profitability). My list is printed out for the cards I have and I will try to find the website where I got the data, as changing those OC settings can have such drastic effects on your mining speeds depending on the algo!