why so many power connectors?
Why not, its just a test board and there's plenty of board space. For the retail boards you just don't dont drop PCI-E connectors through and leave them as empty connections.
I personally would have preferred the chips to be centralised and squashed together more so we could have used standardised PC heatsinks cooling all 4 chips. 350W can be done with one higher end air heatsink or basic 120mm watercooling. I think its time we moved away from these strange aluminium blocks with obscene fans to make up for the low surface areas.
350watt on a "high end" air cooler is going to result in bad temperatures.
With a price of a high end air cooler it would be easier to buy one of those corsair aio water cooling units and have better performance for a price in the same ballpark.
High end air with a sensible fan = will do that fine while being smaller, lighter and cheaper. Either way it doesn't matter because I don't think its what we're getting.