Question about reference card, do they are noisy like the 290 was?
It depends, if you run turbine at 100% speed they are noisy. In normal mining operation, when turbine spins between 40-50%, noise is in acceptable range.
If you are not going to change a BIOS, you are denying yourself quite much of performance boost. With factory BIOS it will be 22Mh/s for 4gb vs. 24Mh/s for 8gb version. Still, i would vote for 4gb reference model.
You are probably generating crazy amount of memory errors. Some cards can do 2000MHz with low mem errors rate, some don't. As stated before -lidag can also help.
Nice results, i was able get only 320Mh/s per potato, tried with a baked potatoes but hashrate was even lower. On the other hand, your cable management is terrible! You need to work on it