According to this PSU rating website you need a minimum PSU for total system wattage of 700 watts using a RX Vega64. PSU REQUIREMENTS - RealHardTechX
Plus you have a high Wattage Ryzen with a TDP of 105 Watts. 2nd Gen Ryzen™ 7 2700X Desktop Processor | AMD
I would go with a High Quality PSU (Bronze or higher) equal to or higher than 850 Watts to cover very heavy loading of the GPU and CPU plus have room to upgrade with a more powerful GPU or CPU in the future.
As to the RAM Memory, you need to go to your motherboard Support site and look at the Motherboard's QVL list for Ryzen 2xxx CPUs to find out if your RAM is compatible with your Ryzen CPU.
Also it is best to purchase and install a RAM MEMORY SET rather than buying separate but identical RAM modules. Most likely, if the RAM are exactly the same in specs, it should work. But you never know with Ryzen CPUs. They are quite sensitive to the type of RAM installed.