With the Xbox One, One X and Series S|X, when you connect them via an Ethernet cable, this takes priority over the wireless adapter and ceases the wireless connection, so you shouldn't need to do anything with wireless settings in the router or the console to use a wired connection on the Xbox. I'm not near my consoles right now to double check, but I'm sure that once connected via Ethernet cable, the wireless options in the console's Network Settings disappear as well. You can't disable the Xbox's wireless adapter via settings, you can either set the console to offline (all or nothing setting), disconnect/forget your wireless network (adapter still active), or plug in an Ethernet cable to give that connection priority over wireless.
Whenever I've used a wired connection with any of my Xboxes, I've never seen them try and use the saved wireless network as well, like it seems your console is doing. That is an odd one.
Side note: Go careful with the Normal/Aggressive WAN setting, as this has nothing to do with devices inside your network and can lead to your device being blocked by the ISP if used incorrectly.
