Gaming may not be Vega's strong suit but that's not to say it can't do at least a respectable job. The whole idea of AMD is to create a product better for a certain price that can do everything you could possibly ask of it (within reason, obviously an R3 SKU for example shouldn't be asked to render a video) at least respectably. Like Ryzen, Vega is a Jack of all Trades.
And what about the RX 560?
It is, but not for editing. I have a 1070 myself.