Typically an ASUS board will have them in in the BIOS under the advanced option.
Gaming boards tend to default into expecting your primary GPU being placed in the primary 16x slot natively.
In addition, you are running the onboard GPU, which implies that is in AUTO, or set by default.
If your intention is to mine with this board and GPUs on risers, you’ll likely need the follow set (CSM may not be an issue with your board):