We haven't seen any factory overclocked custom Radeon RX Vega graphics cards yet, but with SAPPHIRE and PowerColor close to the launch of some new custom RX Vega graphics cards, we might see PowerColor beat SAPPHIRE to the punch with overclocked RX Vega.
PowerColor's upcoming Radeon RX Vega 64 Red Devil graphics card is rumored to ship with a Vega GPU that clocks at 1607MHz, up from the 1546MHz or so that the reference RX Vega 64 and some third-party cards ship with. This is a 3.9% increase over the reference boost, and 1417MHz at base sees a 13.6% increase over base reference GPU clocks.
There is a better triple-fan cooler on a huge triple-slot graphics card, so we should hopefully expect the coolest Radeon RX Vega 64 yet. ASUS couldn't keep Radeon RX Vega 64 that much cooler with their own ROG Strix Vega 64.