You’ll get the best power efficiency and Sols/Watt ratio with NVIDIA GTX 1070 and this miner: NiceHash EQM Zcash NVIDIA optimized miner [Maxwell + Pascal @ Win + Linux] + CPU Mining [v1.0.4c] 400 Sol/s @GTX 1070 (stock)
You’ll get the best power efficiency and Sols/Watt ratio with NVIDIA GTX 1070 and this miner: NiceHash EQM Zcash NVIDIA optimized miner [Maxwell + Pascal @ Win + Linux] + CPU Mining [v1.0.4c] 400 Sol/s @GTX 1070 (stock)