165+ GPU
1000+ MEM
~23.5mh ETH and ~268 SOL/s ZEC each @ ~60W per card.
https://www.youtube.com/watch?v=1uhSfOpvHks&feature=youtu.be&t=7295
Dag won't reach 3GB until early next year, so you should be good until then. The only problem with the 3GB cards you won't be able to dual mine effectivly.
The mining cards that Nvidia will be realsing will be based on the 1060 from what I have read. Mainly just without a video output. I think performance will be similar, maybe ~10% - 20% better and probably cheaper since they only have a 3 month warranty. The Dag is the dataset needed to be stored in memory for the POW mining algorithm used by Ethereum. It grows in size by roughly 0.73x per year. Current size is ~2.1GB and once it exceeds the VRAM on the card, it can no longer proceses the transactions required for mining. Dual mining is a feature where you can mine two diffrent POW algorithms at the same time, therefore incressing the efficiency of mining.
Check out Claymore's ETH miner, that's the only dual miner available and only supports a few select coins.