I have never seen a review from any source that tests what wattage the cable can actually deliver but I could see how handy that may be. I expect the reason they don't do this is down to time constraints. A lot don't even say what wire gauge is used and I had to look through several reviews to find what gauge Seasonic used on the Focus Plus. I thought it would be 16 AWG but all of the main cables are 18 AWG probably to keep costs down on that series. Sadly it's not the first time I have seen connectors melt and we have had several instances on here in the past where the 8 pin or 24 pin connectors to the motherboard have melted (overclocked Bulldozer springs to mind) and a couple with Vega 64 as well. We all know that Vega 64 is a power hungry monster, even more so when overclocked and past threads on here have shown that Vega does have problems being powered from a single lead which are then cured by powering from two seperate leads. Even so, if a psu has the necessary connections on a single lead then it shopuld be up to the job of powering the card without melting.
I got my new psu yesterday, a Aerocool Project 7 650w Platinum which was developed in association with Techpowerup and it has 4x 6+2 pcie connectors. The interesting thing is that they are all on seperate leads which is a first for me on any psu that I have owned as usually they have a pair of daisy chained connectors per lead. Initial thoughts are that it's a solidly built psu. It's reassuringly heavy, silent as the fan only spins up once you hit 60% load, all of the motherboard/cpu cables are 16 AWG while the pci-e, sata and molex are all 18 AWG. It would have been nice if the pci-e cables were 16 AWG as well but I only have a GTX1070 so it's not a problem. The cables are all of the flat ribbon type and are black with black connectors. It has a RGB fan that can be controlled by the motherboard (lead included) but I haven't bothered with that as I have a strong dislike for anything RGB and the fan is facing down anyway.
