Hi,
You would likely need to update the BIOS for the Z370A motherboard to work with the 9700k. The Z370 motherboards will typically ship with a BIOS which are compatible with the 8th Gen intel processors, not the 9th. I would consider either changing the processor for an 8700K which will work with the Z370 out of the box, without the need to update the BIOS OR change the motherboard for a Z390 one, either MSI or Gigabyte Aorus preferably
As for you're power supply, you're definitely good on that front, plenty of power and a really good quality supply too!