It likely will work however you may need to update the bios to the latest version. Some X370 motherboards may need a bios board prior to using a 2700x or the system will not post. Most new x370 boards should ship with this update, but there is a possibility it won't.
I would suggest an X470 or B450 board for out of the box support and they will likely get firmware updates for longer.
Your current motherboard is compatible with an RTX 2070 as long as you have a decent 550w PSU.
Either download it from Gigabyte's website, or use the Gigabyte APP Center.
The GIGABYTE APP Center gives you easy access to a wealth of GIGABYTE apps that help you get the most from your GIGABYTE motherboard. Using a simple, unified user interface, GIGABYTE APP Center allows you to easily launch all GIGABYTE apps installed on your system, check related updates online, and download the latest apps, drivers, and BIOS.