Best PCI-E Setting for My New Graphics Card

You are correct that your G2020 processor provides PCIe 2.0 lanes for video cards.

Using the Auto setting for the PCIe type setting would be the best setting to use when you first connect the video card to the board.

If the video card is not detected using the Auto setting, then change it to PCIe 2.0/Gen 2.

If you have no problems with Auto or PCIe 2.0/Gen 2, you can try PCIe 3.0/Gen 3 as a test. If that fails to work, change back to Auto or PCIe 2.0/Gen 2.

You should check what PCIe speed the video card is using in Windows when using Auto, etc, to be sure you are getting a PCIe 2.0/Gen 2 connection, to get the best performance possible.