attaching 3rd party router

I plan to attach a third party router (AX1800 dual band wi-fi 6 router model Archer AX21) to my TMO-G4AR T-Mobile gateway. Everything ive read seems to say just plug them into each other via ethernet (does it need to be into the WAN port?), make sure you can connect to the new router then use the HINT control app to turn off the broadcast for the 2.4 and 5 ghz , and set them to hidden to prevent any interference on the new Wi-Fi. Am I missing any steps or should this work. I also wanted to know if once I've shut down the broadcast will I be able to turn it back on? The HINT apps says I will need to put a wired connection to turn it back on, but I've also read some reddit posts saying I will still have connection via the new router so I can still turn it on via the app.