New to nVidia mining. Any help will be very appreciated

I am just configuring 2 rigs with 1060 and I cannot get more than 18.8 MH/s on ETH when OCed and not dual mining. How come I am always reading about 22 stock, 25 OCed etc?
What am I doing wrong?
One setup is like this:
4x 1060 3GB, MSI
Win7 pro, 6 GB Ram, some cheap Sempron, 700 W,
this miner (is any other maybe better?), last version drivers.
OC is currently +50 core, +600 mem. If I run them stock, they do only about 15 MH/s
Can you give me your ideas how to push those cards to better hashes?
I am thinking, would Win10 help me? (I tried, but couldnt somehow install nVidia drivers, always got issue with "not for this version of Windows..) Or could Linux help me? (but I dont know if those efficient miners exists for Linux?) Or maybe should I use different miner than this Claymores 9.4 dual?
Thanks
